An intruder who spent 10 minutes in the grounds of Buckingham Palace is a convicted murderer, it was revealed  in the court today

Denis Hennessy was convicted of a savage attack on a homeless man in 1993, which investigators said was like something from the ultra-violent novel A Clockwork Orange.

The 41-year-old, of Wembley, north-west London, climbed over a wall at the Palace on Wednesday evening before being arrested by armed police.

The Queen was in residence with the Duke of Edinburgh and the Duke of York at the time, but Hennessy was stopped in the garden of the iconic building.

Hennessy cut his right hand as he climbed over the top of the wall, which is between 8ft to 10ft high, and set off the alarm.

As he was detained, he asked ‘is Ma’am in?’ repeatedly, prosecutor Tom Nicholson told Westminster Magistrates’ Court today.

In interview he told police he had ‘walked through the gardens admiring the view’. Officers say he was caught seven minutes after the alarm was tripped.

Hennessy pleaded guilty to one count of trespass on a protected site and one count of criminal damage.

The court heard he was on licence after being convicted of the murder of a homeless man in 1993.

Chief magistrate, senior district judge Howard Riddle, today sentenced him to four months for trespassing and two months, to run concurrently, for damaging the wires of the alarm system.

The Queen meets guests during a garden party at Buckingham Palace yesterday, the day after the breach

The Queen meets guests during a garden party at Buckingham Palace yesterday, the day after the breach

Reports from the time of the murder state that Hennessy attacked homeless Kevin Cusack, 45, with an iron bar in Neasden, north-west London.

The victim’s injuries included a ‘flattened’ skull, with virtually every bone fractured. Broken fragments of his dentures were found seven feet away and a senior detective said it was the most gruesome killing he’d seen in 27 years with the police.

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This week’s break-in has led to criticism of security measures at the Palace, with critics saying Hennessy was allowed to wander around the garden for too long after scaling a perimeter wall

Ken Wharfe, a former bodyguard for Princess Diana and Princes William and Harry, said:

‘It took seven minutes to find this guy, which is a hell of a long time. Ten seconds is a long time, a minute is a long time.

‘In 10 seconds you could run 50 yards, at the bottom end of the Palace that would take you into the front door of where the Queen lives, that’s how accessible the Palace is from the perimeter wall at the bottom end.

‘Once somebody is over that wall, unless you catch them immediately there’s no telling where that person might go.’

Ken Wharfe, a former royal protection officer, has criticised royal security officers for the seven minutes it took them to catch Hennessy

Ken Wharfe was a former police guard for Princess Diana

Ken Wharfe, a former police guard for Princess Diana (right) and Princes William and Harry, has criticised royal security officers for the seven minutes it took them to catch Hennessy

The Queen, 90, appeared unfazed yesterday as she hosted the party less than 24 hours after a worrying security breach.

Some 8,000 people, many outstanding members of communities and charities, thronged the palace gardens drinking tea and iced coffee and eating delicacies such as cucumber and mint sandwiches and Eton Mess tarts.

Also accompanying the Queen were Prince Charles and the Duchess of Cornwall, Princess Anne, the Duke of Kent and Prince and Princess Michael of Kent.

Speaking earlier yesterday about the intruder incident at the Palace, Commander Adrian Usher, head of the Met’s Royalty and Specialist Protection, said: ‘I am content that our security measures worked effectively on this occasion and at no time was any individual at risk.’