The three-man team used bolt cutters to force open 55 storage units before they found the arsenal of weapons, which are believed to have been left there by terrorists from a previous operation.
Enough explosives, probably Semtex,and equipment to make a number of bombs are believed to have been removed in the raid. The seizure comes after security services and anti-terrorist chiefs warned that the IRA is preparing a pre-Christmas terror campaign.
A security guard was overpowered and a surveillance camera system deactivated during the break-in, which took place last Friday in Hammersmith, west London. Police last night appealed to the public for help and issued an impression of one of the raiders.
Commander John Grieve, head of the Anti-Terrorist Branch, said: "We have strong grounds to believe that something of considerable value to these men - possibly bomb-making equipment and firearms - may have been removed from at least one of the storage units
"They were looking for something - they knew precisely what they were looking for."
Cmdr Grieve said that evidence left at the scene of the crime indicated that the IRA was responsible. Forensic experts are examining the unit for traces of explosives.
The break-in may be linked to previous anti-terrorist operations. An IRA member, Diarmuid O'Neill, 27, who was shot dead during a series of police dawn raids in west London and West Sussex in September, had worked and lived near to the self-storage units.
The risk and planning involved in Friday's operation suggests that the suspected stockpile must be important to the IRA.
The operation took place at 5.40pm at storage units in Shepherds Bush Place.
The men overpowered and handcuffed a security guard, who suffered from shock and bruising, but was not seriously hurt. They then disabled closed- circuit television and went through 55 of the 200 storage units before finding the suspected bomb-making equipment. The police said the men left a huge amount of debris as they quickly tore through the units, which were individually hired out to store a variety of items, including furniture.
The men, who are believed to have put on fake accents and who wore rubber gloves, removed armloads of heavy objects before making their getaway. The security guard managed to free himself shortly after his attackers left and called the police.
A description of one of the men is of a white male aged 20-25 years, and 5ft 11in in height. He was wearing a black jacket and a dark woolly hat. The other two wore stocking masks. The police are particularly anxious to hear from anyone who may have seen the three men leave the premises and perhaps get into a car.
Cmdr Grieve asked specifically if people had sold a vehicle in suspicious circumstances or if they are renting residential or commercial property to "suspicious tenants". He also asked if people had recently let or re- let storage premises.
He added: "We are in for some dangerous months and it's on the back of that and this strong belief, that this was the work of Provisional IRA that we seek the public's help."Reuse content