Bomb disposal experts carried out a controlled explosion last night on a 250kg World War II shell discovered at Britain’s largest sewage works.

Bomb disposal experts carried out a controlled explosion last night on a 250kg World War II shell discovered at Britain’s largest sewage works.

The bomb was found at Beckton sewage works off Jenkins Lane after surveyors preparing the site for a �200m expansion detected an unusual magnetic force underground on Saturday morning.

The Thames Water workers immediately alerted police and army ordnance experts, who attended the site and confirmed it was an unexploded German warhead.

A 400-metre exclusion zone was set up before the bomb was destroyed at the works under controlled conditions at 9pm on Saturday.

Lawrence Gosden, Thames Water’s head of capital delivery, said: “Every now and again when you’re doing major engineering work like this, particularly in a historic city like London, you come across something a bit odd.

“Most of the time it turns out to be nothing, but we never take any chances

- and in this case we are very glad we didn’t.”

The Germans targeted Newham in the Second World War because it was a centre for imports and the storing of materials.

The bomb was found under an area of open land at the Beckton works which is being prepared for the installation of additional sewage settlement tanks.

The expansion at Beckton is part of a wider scheme to clean up the tidal River Thames.

Thames Water is currently spending �675m upgrading London’s five main London sewage works, one of which is Beckton, so they can treat sewage to higher standards and treat more of it.

Work is also under way on the �635m Lee Tunnel, a four-mile sewer to take to Beckton for treatment the 16m tonnes a year of sewage that currently overflows from Abbey Mills pumping station to the River Lee, a tributary of the Thames.

One of the last UXB’s found in Newham was on the Olympic site in Stratford.