The memorial will be unveiled by the Queen

The �2.3m structure, a large black wall with a cabinet containing a book which names the officers, will be complete in The Mall within four months.

It was organised by the Police Memorial Trust, set up in the wake of the shooting of Pc Yvonne Fletcher outside the Libyan Embassy in 1984.

Founder Michael Winner has campaigned for it to be built for 13 years.

'War with no end'

The film director, who put �500,000 of his own money into the project, said he was "absolutely delighted" that building work was under way.

He said: "I am highly hopeful that people will say: 'The police are out there, dying for us and leaving very distraught families'.

"Memorials to soldiers, sailors and airmen were commonplace. But the police fight a war with no beginning and no end."

Work began on the national monument, designed as a donation by Sir Norman Foster, on Monday.

Donations from individuals, companies and the Police Constables of London have totalled �300,000.