Britain and America spent Wednesday remembering those who died in the US terrorist atrocities of September 11 last year.

Tony Blair joined other senior members of the government, the Royal family, foreign diplomats and families of the UK victims for a service of remembrance at St Paul's cathedral.

Ahead of the service, the prime minister said the nation's thoughts were with those who lost family and friends in the attacks.

"We all witnessed scenes of unimaginable horror," said Blair.

"This week we remember those that died. Our thoughts are also with their families and friends who live daily with the dreadful legacy of these attacks. September 11 was, and remains, above all an immense human tragedy."

Number 10 stressed that the arrangements for the service - co-ordinated through Tessa Jowell and her officials at the Department of Culture, Media and Sport - were agreed with the families of the 67 UK victims.

Jowell and the US ambassador to London, William Farrish, both read lessons at the gathering.

In New York, the Speaker of the Commons, Michael Martin, led the UK delegation at the main service of commemoration in Battery Park.

He also met firefighters and members of other organisations that were involved in the response to the disaster.

Defence secretary Geoff Hoon joined US defence secretary Donald Rumsfeld at the Pentagon, which was also one of the terrorist targets, for a separate service.

A series of memorial ceremonies was held in London, many highlighting the close links with America.

The American Church in London held a service of remembrance and a "One year on" service also took place at St Bride's Church in Fleet Street to remember the journalists and photographers who died.

In the City, the London Metal Exchange, The London international Financial Futures and Options Exchange and Lloyd's of London held a minutes' silence.

In Brussels, the European Union marked the anniversary with flags, anthems and choirs in the entrance to the European parliament.

A ceremony then took place inside the parliamentary chamber attended by leaders of Parliament's political groups, MEPs, EU officials and the US Ambassador to the EU, Rockwell Schabel.