British rapper Dave’s meteoric rise has been boosted by a Mercury Prize win (Ian West/PA)
From a shortlist filled with topical work communicating strong messages on politics, the environment, gender and race, Dave's family reflection was the pick of 2019.
Chosen from the 12 shortlisted artists, Dave was rapturously received by the audience at the Eventim Apollo in Hammersmith, London.
Accepting the award, he said: "I want to thank God. I want to thank everyone, my mum.
"I want to thank my brother Christopher. Even though you can't be here with us today, I know you are watching this bro."
Dave, full name David Omoregie, shared a hug with his mother as he delivered his speech, thanking his sibling, who he said was the inspiration for the album.
Christopher Omoregie was jailed for a knife attack in 2013.
Streatham rapper Dave delivered an emotional rendition of his balladic rap track Psycho, to acclaim from the audience.
He was one of six London artists nominated. Speaking backstage after the win, Dave said: "This is surreal, it is a massive honour, I am glad I have been able to repay the faith that a lot of people have put in me.
"The time, the effort, a lot of people devote their lives to me, every single waking moment of their attention to how I feel, to what I do.
"They respect the craft and the art, so to be able to repay everything they put in, it means the most."
He said he "never expected to win" ahead of a talented field of nominees, adding: "It's the biggest compliment. This is an award that is all about he music."
Dave said his goal now is to make "consistent quality music people can connect with".
Earlier, Slowthai raised eyebrows, bringing an effigy of Boris Johnson's head on stage and declaring "f*** Boris Johnson".
Black Midi gave perhaps the strangest performance of the night with their brand of experimental rock, to rapturous applause.
Little Simz delivered a skilful rap performance while accompanying her own rhymes on the piano.
Stormzy and Jorja Smith were among the judging panel assessing the year's best albums.
The 1975 were nominated for A Brief Inquiry Into Online Relationships, Fontaines D.C. for Dogrel, Seed Ensemble for Driftglass, and Foals for Everything Not Saved Will Be Lost Part 1.
Little Simz was in contention for her album Grey Area, Anna Calvi for Hunter, Idles for their success Joy As An Act Of Resistance, Slowthai for Nothing Great About Britain, Dave for Psychodrama, and Cate Le Bon for Reward.
Nao's Saturn and Black Midi's release Schlagenheim were also nominated.
The Mercury Prize is an honour given to the best album released in the UK by a British or Irish act, and has run since 1992.
Rock act Wolf Alice claimed the prize in 2018 for their album Visions Of A Life.