In a letter to the Home Office, Sir Ian Blair says he refused the Independent Police Complaints Commission access to the crime scene, at Stockwell Tube, where Jean Charles de Menezes died.
He says the Met's counter-terrorism investigation had to take priority.
(...)
"This investigation will be rigorous but subordinate to the needs of the counter-terrorism operation.
"In a fast-moving, multi-site terrorist situation, in which suicide bombers are clearly a very strong possibility,
a chief officer of police should be able to suspend... Police Reform Act 2002 which requires us to supply all information that the Independent Police Complaints Commission may require," he adds.
The IPCC's "duty to provide as much information as it can to the complainant or to members of the deceased's family... could put further lives at risk in these circumstances", Sir Ian says.
"There is much concern about revealing either the tactics that we have and/or the sources of information on which we are operating."
http://news.bbc.co.uk/1/hi/uk/4297532.stmread the letter in full
http://news.bbc.co.uk/1/shared/bsp/hi/pdfs/30_09_05_blair_letter.pdf