Counter-terrorism teams are searching a property in Crawley amid claims that a Briton staged a suicide bomb attack on a prison in Syria.
Officers are examining a house in Martyrs Avenue in Langley Green after reports that a UK jihadi, who used the name Abu Suleiman al-Britani, carried out the deadly bombing.
He is said to have driven a lorry into a jail in Aleppo and detonated a bomb last week, and is thought to be the first Briton to stage a suicide attack in the war-torn state, where increasing numbers of UK-born extremists have gone to fight.
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Before the final declaration on Friday, the Conservative candidate looked set to lose the City Hall race to Labour's Sadiq Khan.
The Tooting MP has been the frontrunner in the counting process ahead of Tory challenger Zac Goldsmith.
It's not just London where elections have been taking place today. There were council elections taking place across the home counties.