Trafalgar Square's fountains turned green for St Patrick's Day as London hosted one of the world's largest celebrations of Irish culture.
Tens of thousands turned out for the parade
Tens of thousands of Londoners and visitors converged on central London for the big parade and festival.
The festivities spread across Trafalgar Square, Leicester Square and Covent Garden and run until 1800 GMT.
London has linked up with Dublin for a weekend-long event and politicians from both countries are also taking part.
Bands included the Metropolitan Police Emerald Society Band and several from Ireland, including St Colmcille's Pipe Band, Arklow, St Maur's, Rush and Bunnoe Bras Band, from Cavan.
Leading the parade was Mayor of London Ken Livingstone, Irish Ambassador Dáithí O'Ceallaigh, Minister John O'Donoghue and Pat Doherty and Dodie McGuinness from Sinn Fein.
Irish Prime Minister Bertie Ahern said: "I am very glad to have this opportunity to send greetings to the Irish community and their friends in London.
"This celebration provides a special opportunity to showcase the Irish community in London."