Three men have became the first people to be charged over the July 7 bombings in London.

Waheed Ali, 23, Sadeer Saleem, 26, and Mohammed Shakil, 30, are accused of conspiring with the four suicide bombers, who killed 52 innocent people.

They are charged with "conspiracy to cause explosions on the transport for London system and/or tourist attractions in the capital likely to endanger life".

Ali and Shakil were arrested at Manchester Airport last month, shortly before they were due to catch a flight to Pakistan, while Saleem was arrested at a house in Leeds.

The trio are all believed to Britons of Pakistani origin who lived in Beeston, West Yorkshire - near Leeds, home to the four suicide bombers.

Ali, also known as Chipon Ullah, only recently moved to Tower Hamlets after living most of his life in Beeston.

The investigation into the bombings was designed to "uncover every possible piece of detail, every clue and lead however minute", Deputy Assistant Commissioner Peter Clarke told reporters at New Scotland Yard.

"Our aim was quite simple, to find out not only who was responsible for setting off the bombs, but also who else was involved.

"As I said in July 2005 we needed to find out who else knew what was going to happen on July 7. Who encouraged the bombers? Who supported them? Who helped them?"

It was "impossible" to convey the scale of the operation, he added. Officers have taken more than 15,000 statements followed 19,000 leads. The search for "every tiny detail" had been "relentless".

The men were under surveillance for some time. DAC Clarke said the decision to arrest two of them was made when they tried to leave the country.

Sue Hemming, head of the Counter Terrorism Commission of the Crown Prosecution Service, said the charges did not relate to the explosions of July 7, "but to earlier planning and reconnaissance before the plot was finalised".

The CPS only decided to charge the three men on Thursday morning.

Over the last two weeks, searches have been carried out at five houses in the Leeds area, as well as at a flat and a separate business premises in east London.

The suspects have been held at the high security Paddington Green police station in London since their arrests on March 23. They are due to appear before City of Westminster Magistrates' Court on Saturday.