What would James Bond do without the ingenious Q, who provides him with all sorts of improbable gadgets for his espionage adventures?

It now seems that Britain's real-life secret agents have a Q of their own after it emerged that they used a fake rock concealing a high-tech communications device to spy on Russia.

In a television programme aired on Russian state television in 2006, Russia's FSB security service accused Britain of using the gadget for top secret communications in Moscow, but London did not admit to the charge at the time.

Now Jonathan Powell, who was chief of staff to then Prime Minister Tony Blair, has confirmed the Russians were correct.

They had us bang to rights, Powell says in a BBC documentary to be aired on Thursday.

Clearly they had known about it for some time and had been saving it up for a political purpose, he says in an excerpt played on BBC radio ahead of the broadcast.

Relations between London and Moscow were tense at the time because of disagreements over the war in Iraq, Chechnya, and a British court's refusal to extradite businessmen and Chechen leaders wanted by Russia.

There's not much you can say. You can't really call up and say 'terribly sorry about that and it won't happen again', Powell says.

As well as exposing the dummy rock ploy, the 2006 Russian programme said Britain was covertly funding Russian pressure groups that were subject to a state crackdown. Britain said it was open in its support of Russian NGOs active on human rights and civil society issues.

Espionage scandals were a staple of British-Russian relations during the Cold War. Although they are less frequent nowadays, ties between the two countries have been strained in recent years by allegations of covert operations.

In particular, Russia enraged Britain with its refusal to extradite an ex-KGB man who is the main suspect in the 2006 murder of Alexander Litvinenko, a Kremlin critic who was poisoned by radioactive polonium in London.

The Russian television programme showed footage of a man struggling to pick up a rock from a snowy roadside in Moscow before walking off with it -- a real-life replay of the dead letter drop of spy novel fame.

The man was accused of being a British spy and the rock was described as a fake that contained a device capable of receiving information electronically and beaming it to a hand-held computer.

The FSB said four spies working undercover as diplomats at the British embassy in Moscow had made use of the device.

They would have made Q proud -- if only they hadn't got caught.

(Reporting by Avril Ormsby, writing by Estelle Shirbon)