The Prime Minister and the Prince of Wales joined families and friends of the 67 Britons who died 10 years ago in a remembrance ceremony.
The main anniversary event in the UK was held at the September 11 Memorial Garden next to the American Embassy in Grosvenor Square, London.
About 30 of the bereaved British families attended the remembrance ceremony in the garden, at which the names of the victims were read out and a white rose laid for each one.
Another memorial service was held at St Paul’s Cathedral, where worshippers prayed for the nearly 3,000 people who died in the attacks, while at Westminster Abbey there was a service of remembrance and reconciliation.
Relatives of about 10 UK victims have travelled to New York for the events organised by the US authorities at Ground Zero, the former site of the World Trade Centre.
Britain suffered more losses in the September 11 2001 attacks on New York and Washington DC than any other country apart from America itself.