On Thursday, the British capital led the tributes for the 52 victims with workers leaving their offices to stand in the street.
Taxis and buses pulled over and financial markets paused to remember the dead.
Queen Elizabeth stood in silence at Buckingham Palace. In London's Trafalgar Square, a giant banner declared "one city, one world".
In Italy, government offices, railway stations and airports paused while television stations cut into normal broadcasting to honour the London dead.
Pope Benedict prayed for an end to terrorism during his holiday in the Italian Alps.
Berlin's transport authority ordered buses, trams and underground trains to halt for two minutes.
And in Paris, President Jacques Chirac's annual Bastille Day television address was delayed so the French could mark the moment. Chirac stood in silence on the steps of the Elysee Palace.