Serial burglar swanned into Downing Street using Lithuanian lover's ID in amazing security breach

Drug addict Obadiah Marius calmly walked though a series of rooms near the back of No 10 dressed in a track suit and T-shirt.

The breach took place at a time of heightened security with MI5 rating the threat to the UK as "critical", and only three weeks later there was a terror attack at Glasgow airport.

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'Persistent rogue': Obadiah Marius with Lithuanian girlfriend Victoria in East London

Yesterday Marius was described as "a persistent rogue" when he appeared before Judge Christopher Hardy for sentence. But he escaped a jail term.

Marius and his Lithuanian girlfriend Victoria Vaitekunaite, 20, approached the entrance to the Cabinet Office at around 6pm on June 5 last year.

Prosecutor Isobel Ascherson told Southwark Crown Court they entered the complex at No 70, Whitehall, and, according to one security guard "Marius may have held up what I believed to have been a building pass".

A main door was either "unlocked for him" or may not have been properly closed in the first place. "He kept it open and was followed through by his girlfriend who was carrying a plastic bag,' said the prosecutor.

The couple then walked through a door marked "Ministers".

Miss Ascherson added: "They went upstairs where there were a number of offices unmanned and nobody to be seen. It was quite an astonishing breach of security and these two people were at loose in the Cabinet Office.

"They came back down and went to a side door which brought them out to number 9 Downing Street, near the Privy Council office, where security saw them and immediately challenged them."

The prosecutor said the pair insisted they were looking for work. Armed police searched the offices to see what they may have left behind.

The couple were also searched, and officers found the girlfriend's Lithuanian identity card.

Judge Hardy asked if there had been a "full inquiry into this breach of security".

"I would hope so, your honour," Miss Ascherson replied.

Marius, from Stratford, East London, had 78 previous convictions and had appeared in court 36 times. His first offence of theft took place when he was 13 and in 1977, at 15, he committed his first burglary. The court heard that he stole to fund a drug habit.

Yesterday Marius admitted the Downing Street break-in. He also admitted breaking into Snaresbrook Crook Court on March 16 last year, and stealing three judges' laptops worth £4,500.

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Security breach: Route that led Marius's took in Downing Street break-in

On that occasion Marius walked into an empty courtroom and then into the secure area reserved for judges.

Caught on CCTV cameras, he was arrested the following month but had sold the laptops.

Passing sentence yesterday, Judge Hardy said: "The bulk of your life has been spent in prison because at an early age you were foolish, unwise and stupid enough to get involved in drugs.

"You stand before this court a dishonest and persistent rogue. In June, through an appalling lapse in security which one can only hope has been remedied, you entered the very heart of Government - Downing Street.

"You entered various offices and, although nothing was stolen there, it is quite clear your purpose was to steal anything you could find."

Th judge told Marius he deserved to go to prison but noted that he was still committing crimes despite many previous terms in jail.

The judge said probation reports suggested he was prepared to undertake a residential drug treatment course in Devon. By leaving London he might be helped by being away from drug taking associates in the capital.

He gave him a 12-month prison sentence, suspended for 18 months, but with an 18-month supervision order and a year-long residential drug rehabilitation order.

Miss Vaitekunaite was charged over the Downing Street break-in but was cleared after the Crown offered no evidence.