All 30 Britons killed in the Tunisian beach attack have been identified, Foreign Secretary Philip Hammond has said.
It came as the bodies of more victims were flown back to Britain, nearly a week after Seifeddine Rezgui opened fire in the resort of Sousse.
Tunisian authorities have arrested a number of people suspected of having links to the massacre.
Met Police chief Sir Bernard Hogan-Howe said that one of the objectives of today's terror training exercise in London is to "learn from the mistakes we're bound to make."
"Best we make them today in an environment which we don't have terrorists that make them when we do," he said.
Stories continue to emerge of the heroism and compassion of Tunisians who tried to help in the wake of the Sousse attack.
Seifeddine Rezgui was halfway through a Masters degree and took exams at the Institute for Applied Science and Technology before the attack.
As details of the dead continue to surface, James Jordan met Mohamed Sabhi, who ran towards the carnage to shepherd tourists to safety.