Killer's 82-second rampage brought death to streets of WestminsterSecurity services don't yet know the content of terrorist's encrypted WhatsApp message
At the Preston Park Hotel in Brighton on Wednesday morning, Adrian Ajao was chatting with hotel staff about his plans for the day as he checked out at reception.
"I'm off to London today," he told them as he handed over his credit card, before adding: "It isn't like it used to be."
The 52-year-old had spent the night in room 228 at the budget hotel, eating a takeaway kebab as he made his final plans for what would be the UK's most murderous terrorist attack since the July 7 suicide bombings in London in 2005.
He had checked in at 11.30am on Tuesday, and tried to negotiate a cheaper rate than the £59 he ended up paying, but the staff found him so pleasant that they wrote "nice man" in the notes on his computer booking.
During his brief stay he chatted to staff about his parents, who live in Wales, saying he was worried about his father, who has cancer, and his mother, who was struggling to cope.
He was "nice, polite and calm" according to one hotel worker, and raised no suspicions among staff.
The hotel's manager, Sabeur Toumi, said he was "laughing and joking, telling us stories about where he lived".
The only oddity about his stay was that after he had checked out and put his two bags into his Hyundai hire car, a cleaner found him back in his room in just his underwear. The reason for this remains a mystery.
Sixty miles away, London was its usual bustling mix of workers and tourists.
In Westminster, parliament was sitting, with a morning of debates preceding Prime Minister's Questions.
Among those looking forward to PMQs was 19-year-old politics student Travis Frain, who was on an "ideal" day out touring the Palace of Westminster with university friends.
Across the river, Spanish teacher Aysha Frade was in the middle of lessons at DLD College near Waterloo Station. Westminster Bridge was bustling with tourists, taking pictures of each other with Big Ben behind them.
For Ajao, the bridge and parliament itself - or rather the people using them - amounted to only one thing: targets.
Despite his personable demeanour, Ajao, who was born Adrian Elms to a white mother and black father before his mother married and changed his name to Adrian Ajao, had a history of criminal convictions for violence and had twice been jailed.
He converted to Islam and changed his name to Khalid Masood, coming to the attention of MI5 when he started mixing with known extremists. Far older than the average jihadi, he had slipped off the radar and was assumed not to present a danger to the public.
As Ajao drove towards London, PC Keith Palmer was beginning his shift guarding Carriage Gates, the vehicle entrance to Parliament, where at 2pm he posed for a picture with American tourist Staci Martin.
By 2.35pm Aysha Frade had left work at DLD College to walk across Westminster Bridge on her way to pick up her two daughters from school.
Meanwhile at 2.37pm, Ajao was pausing to send a final message to someone via the mobile messaging service WhatsApp. Whom he was messaging, and the content of the message, has not yet been released by the police, but it is likely to be a vital clue in the hunt for accomplices.
However, police are expected to have difficulty accessing the contents, which were encrypted, and cybersecurity experts say they will have to employ their own hackers.
It was just after 2.40pm that Ajao, in the grey Hyundai Tucson 4x4, appeared on the eastern approach to the bridge, two large kitchen knives by his side. He mounted the pavement, reaching more than 40mph, and would take 30 seconds to cross the 250-yard span of the bridge.
More than 40 people would be killed or injured in those few seconds, mown down as they walked across one of the capital's busiest river crossings.
Americans Kurt and Melissa Cochran, on the last day of a holiday in London to celebrate their 25th wedding anniversary, were just about to cross the bridge. Musician Mr Cochran, 54, was hit by the car and thrown on to a walkway 15ft below which led to the river bank, becoming the first fatality.
As he lay on his side, one leg clearly broken and with blood seeping on to the paving stones, passers-by ran to his aid, the first of the day's many heroes.
Melissa Cochran (46) had also been hit by Ajao's car and suffered injuries including a broken leg and rib. She appeared to have been thrown to one side, hitting a postcard stand on the corner of the bridge and the riverbank.
A photo of her lying on the pavement, bloodied postcards scattered around her as she stared, terrified, into a camera lens while a woman in a long grey coat knelt and held her head, would become one of the most haunting images of the day.
Ajao was only just beginning two minutes of carnage. Pressing the accelerator hard down and staying on the pavement, he drove at murderous speed, as CCTV footage later showed.
As well as Britons, the pedestrians skittled by his car included four South Koreans, three French children, two Romanians, two Greeks and one each from Ireland, Germany, Poland, Italy, China and America. Three of them were police officers on their way back from a bravery award ceremony.
PC Kris Aves, 35, who had been honoured for his "exceptional" work as a family liaison officer, suffered "life-changing injuries" that later required eight hours of surgery.
Speaking from his bedside, PC Aves's family said he had been "full of pride". His colleague PC Roger Smith, aged in his early 50s, also suffered leg injuries that required surgery, while Pc Bradley Bryant escaped with minor injuries.
A group of French schoolchildren from Lycee Saint-Joseph de Concarneau in Brittany were on a school trip to London when Ajao's car bore down on them.
One of them, called Thomas, suffered a head injury and fractured legs. The children, aged 15 to 16, were all later taken to hospital. Thomas's mother said: "My husband and I thought he was dead. After an hour we were told he was injured. It felt like an extremely long time."
Travis Frain, fresh from watching Prime Minister's Questions, was walking across Westminster Bridge when he was hit and went over the bonnet of the Hyundai. Despite suffering a fractured leg, fractured left arm, two broken fingers and flesh wounds, he still managed to call his mother Angela as he lay in pain to say: "Mum I'm safe."
Francisco Lopes, 26, from Portugal, suffered leg and hand injuries when he was hit by the car. He said: "He started to move towards the pavement and started to just take out the people that were in front of the car, so, when I realised this, the car was literally just about one metre away, so I had no time to get out of the way."
Further along the bridge, Mrs Frade was about to become the second person to lose their life. She was hit by Ajao's car and thrown under the wheels of a bus, dying at the scene.
Around 100m further along the bridge, Ajao's speeding car closed in on Romanian architect Andreea Cristea and her fiance Andrei Burnaz. They were in London to celebrate Mr Burnaz's 33rd birthday and to buy a wedding dress. Mr Burnaz's foot was crushed by the car and his 29-year-old girlfriend was badly injured as the vehicle forced her over the side of the bridge into the River Thames 30ft below.
Mr Burnaz screamed down to boats below for someone to save her, and as Miss Cristea bobbed to the surface, face down and apparently unconscious, the captain of a pleasure boat tried to pull her onboard with a boat hook after she passed under the bridge.
The crew of the City Cruises boat were unable to get her out of the water, but stopped the boat and held her fast to the side to stop her being swept downstream until a nearby fire service boat which was on an exercise pulled up alongside and rescued her.
Next to be hit was a group of South Korean tourists, four of whom are still in hospital, then a man dressed in a business suit who was pictured lying on the pavement with one shoe off, blood pooling around his ankle.
Elsewhere on the bridge, pest controller Keith Chapman (61) was on his way to carry out some work at St Thomas's Hospital when he was thrown up in the air and his leg "smashed to pieces".
Another of those hit was retired window cleaner Leslie Rhodes (75) from Streatham, south London, described as a "lovely man who would do anything for anybody" by neighbours. For many years he cleaned the windows at Chartwell, Winston Churchill's former home in Kent. Mr Rhodes suffered catastrophic injuries and died in hospital the following day when life support was withdrawn.
On the bridge, Ajao jerked the steering wheel to the right to avoid hitting a concrete barrier at the western end of the pavement built to protect pedestrians. He appeared to lose control of the car, veering to the left, back on to the pavement on the other side of the concrete barrier, hitting two more pedestrians before crashing into railings around the perimeter of parliament.
Rick Longley was walking towards Westminster Underground station, opposite the scene of the crash, when he heard a loud bang just before 2.41pm, followed by a scream.
Ajao had got out of the car with his two knives, and ran around the corner into Parliament Square. Around a dozen people, running for their lives in front of him, made for the sanctuary of Parliament's New Palace Yard, getting in through an open vehicle gate manned by two unarmed officers.
One of them was PC Palmer (48). Mr Longley said: "A guy came past my right shoulder with a big knife and just started plunging it into the policeman.''
As PC Palmer staggered away, Ajao headed towards the door of the ancient Westminster Hall. Sitting in a ministerial car a few yards away, the Defence Secretary Michael Fallon's police protection officer had seen the stabbing and was quickest to react. Striding towards Ajao, he waited until he was 6ft away from the terrorist, raised his pistol and shot him three times in the chest.
Among those who witnessed the attack on PC Palmer was Tobias Ellwood, the Foreign Office minister and former soldier. He tried to staunch the blood, and when he could find no pulse he tried to keep the officer alive with mouth-to-mouth resuscitation and chest compressions.
A few yards away, policemen tried to save the life of Ajao while simultaneously stripping him to check he was not wearing a suicide bomb or concealing another device. The terrorist's bare legs kicked in agony before he became still and unconscious.
Inside the House of Commons, there was further drama. Prime minister Theresa May and other MPs were in the voting lobbies, voting on new pension legislation, when armed police burst in, guns raised, splintering the wooden doors. Over their walkie talkies, colleagues were shouting "there's been a bomb, there's been a bomb!".
At 2.45 the sitting in the House of Commons was suspended. MPs were locked in the chamber and told to stay there, but Mrs May was whisked away by her protection officers to her silver Jaguar parked outside in Speaker's Yard.
Mobile phone footage showed the prime minister briefly running the wrong way before being ushered to the car as an officer shouts: "Get in the car!"
Another member of her security detail shouted for his car keys, the tension of the moment abundantly clear.
Mrs May had to be driven along a service road that runs the length of Parliament, emerging at the opposite end to New Palace Yard before being taken through back streets to Number 10.
An air ambulance landed in Parliament Square and its paramedics ran to take over the life-saving efforts.
Moments later, two ambulances drove in through the gates. One of them took Ajao to hospital, where he was pronounced dead. The other waited to take PC Palmer to an operating theatre - but he never made it as far as the ambulance.
As Tobias Ellwood stood slumped with exhaustion, PC Palmer's blood smeared on his face, hands and cuffs, PC Palmer was pronounced dead at the spot where he lay.
The police officer will be remembered permanently at the National Memorial Arboretum, UK Home Secretary Amber Rudd said yesterday.
Police confirmed that the attack lasted 82 seconds. Deputy assistant commissioner Neil Basu, the senior national coordinator for UK counter terrorism policing, said: "We still believe that Masood acted alone on the day and there is no information or intelligence to suggest there are further attacks planned.
"We must all accept that there is a possibility we will never understand why he did this.
''That understanding may have died with him."