British forces in Iraq have seized a two-ton cache of weapons - including rockets, grenades and bomb-making equipment - belonging to the gang responsible for the deaths of numerous servicemen.
The discovery, which military commanders believe is the most significant breakthrough since they arrived in Iraq in 2003, followed the arrest of the leader of the fundamentalist Shia group in Basra last weekend.
Des Browne, the Defence Secretary, told The Daily Telegraph: "We got a very important person, the leader of a very dangerous militia gang, which will lead to a very significant deterioration in their capability � This is a sign of significant progress."
Mr Browne said Sajjad Badr Adal Saeed, the Jamaa leader who ordered the killing of many British soldiers in roadside attacks, was taken from his home in Basra last Saturday night. Ordnance tactics handbooks, fake IDs and detonators were found.
"This man was a very significant leader," Mr Browne said. "He was a planner, but he also had technical abilities which were very valuable to the militia."
Three days later, British forces used intelligence gathered at the address to track down the weapons cache and bomb-making factory.
Ministry of Defence sources said more than 50 rockets, about 10 rocket-propelled grenades and 150 mortars were seized following a battle. Improvised explosive devices - the roadside bombs that have killed so many British soldiers - were also found, fully assembled, along with mines and other weapons.
One source said: "This is the largest cache we have found in two years." Saeed was "the most significant guy arrested in Iraq" by British forces.