A cluster of 52 rough-cast stainless steel columns was opened in London’s Hyde Park on Tuesday, the fourth anniversary of the 7/7 bombings which they commemorate.

The memorial is an ingeniously simple, starkly elegant composition, with each column representing a victim. The four separate bomb sites (Underground stations Russell Square, Aldgate and Edgware Road and a bus at Tavistock Square) are picked out in four subtle shifts in the grid on which they stand.