London will lead the two-minute silence at midday (1100 GMT) on Thursday, as traffic and businesses stop, flight take-offs are delayed and even hospital workers, treating the wounded from the blasts, bow their heads.
"London will remember all of those who died last Thursday and show its defiance of those who try to change the character of our city through terror," Mayor Ken Livingstone said.
"London will not be moved from our goal of building an open, tolerant, multi-racial and multicultural society showing the world its future," he added.
The multiple blasts on three underground trains and a double-decker bus plunged into shock and grief a city that 24 hours earlier had been celebrating being awarded the 2012 Olympic Games.
Ryanair, Europe's leading low-cost airline, said it had seen forward bookings drop 10% in the four days following the London bombings.
But Britain's capital city will not be alone, the solemn moment will be marked in towns and cities across Europe in recognition of the multiracial nature of the dead and maimed.
Bourses around Europe said they would mark the occasion, and the 134th British Open golf tournament in Scotland will also halt play.