Nobel Prize-winning scientist Professor Peter Higgs has revealed he first heard he won the prestigious award when a women stopped to congratulate him in the street.
Prof Higgs said a former neighbour, the widow of a judge, got out of her car in Edinburgh as he was returning from lunch and introduced herself.
"She congratulated me on the news and I said 'oh, what news?" he told a press conference at the University of Edinburgh.
"She told me her daughter phoned from London to alert her to the fact I had got this prize.
"I heard more about it obviously when I got home and started reading the messages."
The existence of the so-called ''God particle'', said to give matter its substance, or mass, was proved 50 years on by a team from the European nuclear research facility (Cern) in Geneva, Switzerland, in 2012.
Giving his reaction to the prize for the first time, he said: "How do I feel? Well, obviously I'm delighted and rather relieved in a sense that it's all over. It's been a long time coming."
An old friend told him he had been nominated as far back as 1980, he explained.
Prof Higgs said he had been having lunch in Leith in the Scottish capital when the announcement was made on Tuesday.
Describing the low-key way he learned of the prize, he told the assembled press he was walking up Heriot Row in the New Town when the former neighbour spoke to him.
But there will be a champagne celebration with family this evening.
"There was a celebration with a group of us last night after a lecture by Frank Close - that was a start," he said.
"I shall be celebrating with my family with the help of a bottle or two of champagne early this evening.
"It hasn't been possible to get us all together before that."
The 84-year-old is an emeritus professor at the University of Edinburgh.
The Swedish prize was established by businessman Alfred Nobel and was first awarded in 1901 to honour achievements in science, literature and peace.
The Higgs-Englert award recognises the ''theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles''.
That mechanism predicted the existence of the Higgs boson, which enables particles to acquire mass.
Its discovery is of huge significance to the theory that enables scientists to understand the physical universe, known as the Standard Model of Physics.
Prof Higgs established the concept of the ''God particle'' while working as a lecturer in 1964.
He wrote two scientific papers on his theory and was eventually published in the Physical Review Letters journal, sparking a hunt for the elusive particle.
Other researchers, including Prof Englert, were also working separately on the same idea as Prof Higgs and published papers around the same time.
A new particle "consistent" with the Higgs boson was discovered last year by a team at the Large Hadron Collider at Cern, the European Organisation for Nuclear Research, near Geneva.
Prof Higgs said he celebrated on the return flight from Cern last year with a bottle of London Pride beer, which he was presented with during today's press conference.
He said: "I think I face the immediate future with some foreboding because having experienced the wave of attention which followed the announcement at Cern in July 2012, I anticipated that this last announcement will trigger an order of magnitude of more attention.
"I think I am going to have difficulty in the next few months having any of my life to myself."
He stressed the involvement of other theorists and Cern.
"I think clearly they should, but it is going to be even more difficult for the Nobel Committee to allocate the credit when it comes to an organisation like Cern," he said.
"I should remind you that although only two of us have shared this prize, Francois Englert of Brussels and myself, that the work in 1964 involved three groups of people, (including) two in Brussels.
"Unfortunately Robert Brout died a few years ago so is no longer able to be awarded the prize, but he would certainly have been one of the winners if he had still be alive.
"But there were three others who also contributed and it is already difficult to allocate the credit amongst the theorists.
"Although a lot of people seem to think I did all this single-handed, it was actually part of a theoretical programme which had been started in 1960."
Prof Higgs was made a Companion of Honour in the New Year Honours list and the Higgs Prize has been set up by the Scottish Government to recognise school pupils who excel in physics.
He was joined at today's event by Edinburgh University principal Professor Sir Timothy O'Shea and Dr Victoria Martin, a reader in the School of Physics and Astronomy who works with Cern and is a former student of Prof Higgs.