PC Nina Mackay, 25, was in a group of officers who forced their way into a flat in Stratford, east London, on 24 October last year to search for Magdi Elgizouli, who was in breach of his bail conditions.

Nina Mackay: Died despite attempts to save her life

She died in hospital after a desperate fight to save her life. Her 30-year-old killer was later sent indefinitely to Rampton top-security mental hospital after admitting manslaughter on the grounds of diminished responsibility.

The 3ft-high granite memorial at the spot where PC Mackay died has been erected by the Police Memorial Trust and is the 22nd such tribute since the foundation of the Trust in 1984.

Mr Blair's wife, Metropolitan Police Commissioner Sir Paul Condon and Memorial Trust Chairman, the film director Michael Winner, were also present.

The prime minister spoke of his shock on hearing news of her death in Downing Street.

He told around 300 officers and friends of the dead policewoman: "It was deeply shocking and as we read and learnt more about Nina, the shock became more personal to us.

Magdi Elgizouli: Detained indefinitely

"She was by all accounts a remarkable young woman. She was open and vivacious, extremely strong and determined in what she wanted to do." PC Mackay's memorial bears the badge of the Metropolitan Police and the simple inscription: "Here fell PC Nina Mackay, 24th October 1997".

She came from a family with a strong tradition of police service. Her father was a chief superintendent and her brother is a member of the Metropolitan Police's tactical firearms unit.

At the time of her death, PC Mackay had five years service with the Metropolitan Police. She was single, had no children and lived alone in east London.