The device - which was the biggest found in London since 1975 - contained more than 1,000 kg of explosive.

Soldiers from the 33 Engineer Regiment of the Royal Engineers had been carrying out a detailed and delicate operation to defuse it since Monday when it was unearthed near the River Lea by workers widening the bank to take barges for the 2012 Olympics site construction.

The Army worked in shifts around the clock. They used nearly 400 tonnes of sand to build a structure around the bomb to contain the blast effects if it had detonated. It was finally dealt with on Friday evening with a controlled explosion.

Sir Robin said: "We owe all the Army engineers a massive thank you for what they did. We should all be very, very grateful and we will be looking to recognise that fact in a more public way in the very near future."

The Mayor was allowed just inside the 200-metre evacuation zone on Friday to see how the Army, police and emergency services and the council's own emergency planning and resilience team had been dealing with the problem.

Said Sir Robin: "The fact they have dealt with such a potentially dangerous situation with a minimum of disruption to local people has been nothing short of incredible. Everybody has taken the needs of the community into account and this has been a real combined effort.

"The engineers told me that this was a particularly tricky operation because the bomb had a solid explosive material instead of powder and that it had to be steamed out. It also had a booby-trapped timer and tamper devices.

"The 33 Engineer Regiment was born out of the Royal Engineer Bomb Disposal companies, formed during the Second World War to deal with the mounting problem of German unexploded bombs. They told me that one in ten of air dropped ordnance did not explode. A situation like this really puts the value of their work into perspective."