A service is being held at St Paul’s Cathedral in memory of the 52 people killed by suicide bombers in London on 7 July 2005.
Survivors of the attacks and relatives of the victims are among those at the event.
Many people across the UK will observe a minute’s silence at 11:30 BST.
Earlier, PM David Cameron and London Mayor Boris Johnson were among those who laid wreaths in Hyde Park – where another service will be held later.
The bombings of three Tube trains and a bus – carried out by four bombers linked to al-Qaeda and carrying rucksacks of explosives – was the worst single terrorist atrocity on British soil.
More details on the BBC Website: 7 July London Bombings: Servie to remember the victims