Around 150 intact memorial brass plaques with inscriptions commemorating the lives of loved ones, complete with stakes and plugs still attached from where they had been pulled out of the earth and ripped off walls.

Numerous pieces of hundreds more plaques thrown into boxes nearby.

Two metal cutting machines were found inside the premises.

Scotland Yard has already been able to identify at least 40 as having been stolen from a Beckenham crematorium.

Inquiries to trace the origin of the other plaques continue.

• Foreign criminal syndicates 'behind metal thefts in Britain'

  31 Mar 2012

• Czech metal thieves dismantle 10-ton bridge

  30 Apr 2012

A distinctive bronze dragon statue set in concrete and weighing around a tonne, worth around £3,500, had been stolen from a couple in Teddington.

Police also seized £20,000 in cash and copper cabling from the yard.

The yard was one of number targeted in boroughs across London in the highly targeted two day operation on Monday and Tuesday, which saw a total of ten arrests, a significant number of stolen vehicles recovered, and fixed penalty notices issued for waste offences.

Thieves have been posing as BT engineers, wearing high-visibilty jackets and forging job sheets and passes, to steal hundreds of metres of copper cable.

Police figures show that since the start of March this year show that there at least 100 metal theft related offences reported to police in the capital each week.

Metal theft is estimated to cost at least £700 million a year to the economy and an increasing variety of objects are being targeted, from cable, drain covers, lift panels from housing estates and war and cemetery memorial plaques, to children's playground slides, fire escape stairs and even English Heritage buildings.

Acting Inspector James Coomber, the operation coordinator, said: "This represents a significant find in our ongoing efforts to target metal theft.

"The majority of scrap metal dealers who are legitimate support our targeting of those acting outside of the law. Those contributing to the thriving illegal trade can expect regular operations to search, detect and arrest those profiting from it.

"We are focusing our resources on yards where intelligence leads us to believe they are taking in stolen metal, not recording items lawfully, and committing related offences. Metal theft is not a victimless crime and the public can play a vital part helping us by reporting anything suspicious to us.

"Don't assume if you see workers in the street with cable that they are legitimate, even if they are in high visibility vests, and watch out for itinerant collectors who come door to door as we know a number of these are involved in domestic metal theft, for example lead from roofs of houses.