Reyaad Khan was helping to plan a coordinated attack on the capital when he was killed by the RAF in Syria at the end of August in an operation personally sanctioned by Prime Minister David Cameron.
Khan, from Cardiff, was killed alongside Ruhul Amin, 26, from Aberdeen.
The strike took place without approval from Parliament but the Government argued it was legal as an act of self-defence and the only way to prevent terror attacks on British soil.
A well-placed security source has told the Sunday Express that Khan, 21, was a bridge between Islamic State and its supporters in Britain.
Working with IS sleeper cells here, he was organising support and logistics for fanatics to hit several targets in a chilling echo of the Charlie Hebdo massacre in January and a grim forerunner of what would happen in Paris.
However, a drone blew up the car he was in as he phoned an associate in the UK after meeting his chiefs in Raqqa.
Khan, who harboured dreams of becoming Britain’s first Asian prime minister before he was radicalised, had earlier tried to mastermind another plan to kill the Queen and other senior Royals during VJ Day commemorations in London.
Both plots were referred to by Mr Cameron in a speech to the House of Commons in the aftermath of the November 13 attacks in France in which 132 people were killed.