The monster, born Adrian Elms, beams for the camera in a photo as he lines up with school mates before taking part in a charity football competition.
Masood, sixth from the left, is aged around 15 a pupil at Huntley Secondary School in Tunbridge Wells, Kent, when the photograph was taken in the early 1980s.
By this time he was known as Adrian Ajao after taking on the surname of his stepfather Philip, who is believed to be of Nigerian origin.
Over the next four decades Masood, 52, led a chaotic double life.
In prison he was radicalised by other inmates and converted to Islam
He lurched between being a polite family man who worked as a teacher living in country villages to holing out in squalid bedsits in Muslim ghetto areas of Birmingham, Luton and London.
It was after leaving school that Masood’s life appeared to go off the rails, when he began dabbling in drugs before getting involved in petty and violent crime.
He was 18 when he first fell foul of the law and was convicted for criminal damage.
Khalid Masood made the transition from a football-mad teenager to the hate-filled jihadi terrorist London terror attack: Latest pictures Fri, March 24, 2017
4 dead and 40 injured in London terror attack
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Armoured police personnel carriers are seen on a street leading to the Houses of Parliament in central London on March 24, 2017 two days after the March 22 terror attack on the British parliament and Westminster Bridge
He went on to receive a string of convictions.
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The Daily Express can reveal that Masood, who had always felt an outsider because of his ethnicity, finally snapped after an incident involving “racial overtones” when he slashed the face of a cafe owner Piers Mott with a knife which left a three inch gash in his cheek in his village.
It led to him being jailed for two years at Hove Crown Court in November 2000.
Neighbours in Northiam, West Sussex, told how Masood became radicalised during his time in prison.
He had lived in the village with his chemical firm boss partner Jane Harvey and their daughters now aged 22 and 16, in a smart three-bedroom bungalow.
Locals said relations with villagers turned sour after the couple were involved in a dispute over a development of garages.
Masood admitted charges of unlawful wounding and criminal damage after he also slashed a car belonging to Mr Mott.
Khalid Masood on a stretcher after launching his terrorist attack in Westminster
Khalid Masood, born Adrian Elms, in a photo with school mates before a charity football competition
One villager said: “In prison he was radicalised by other inmates and converted to Islam.
"He became a real extremist.
"When he got out of prison he decided he wanted to live an Islamic life and didn’t want anything to do with his past life.
"He left his partner and the girls and went to live in some dump in Eastbourne and I think he met someone else.”
In 2004 he is understood to have married a Muslim, Farzana Malik. It is unclear what became of their relationship. By 2005 he was working in Saudi Arabia teaching.
It is thought concerns over his radicalisation came to the attention of MI5 after his return.
It’s believed he received visits from the police in 2006 when he was living in Crawley. In 2008 he was back in Saudi Arabia before returning in spring 2009.
After a five-month gap, he is said to have joined a college in Luton as a “senior English teacher”.