7/7 anniversary: 'We are in a critical terrorist environment'

A service will take place at St Paul's Cathedral later to mark the 10th anniversary of the 7 July terrorist attacks that killed 52 people in London.

The attack - by four suicide bombers linked to al-Qaeda and carrying rucksacks packed with explosives - was the worst single terrorist atrocity on British soil.

Michael Clarke, from the Royal United Services Institute - an independent think tank specialising in defence and security - says we live in a "critical terrorist environment", but we should carry on with our lives as normal.