An intruder has admitted breaking into the Houses of Parliament in a major security blunder.

Trespasser Devon Dorrall dodged round-the-clock guards and armed police to sneak into the heart of the London estate undetected at lunchtime on November 30 last year.

He was discovered sitting on a chair in the Mess area of the House of Lords – an incident not disclosed by authorities at the time.

The 23-year-old from Tilehurst in Reading was charged with trespass on a protected site.

He pleaded guilty when he appeared at Westminster Magistrates Court today.

He will be sentenced in June.

The court heard he had previously been referred to the Government’s Prevent anti-terror programme, although no further details were aired during the 12-minute hearing.

Prosecutor Olivia Grist said medical reports suggested Dorrall was suffering a psychotic episode at the time, but it was ‘more likely than not’ that this followed the consumption of illegal drugs.

Devon Dorrall admitted climbing over a roof to get into the House of Lords last year

She told the court: ‘He entered the Mess in the Lords and was believed to have not been allowed to be there.

‘Staff approached the defendant and saw him sat on a chair.

‘He was not engaging with staff or police, and stared in a manner that was threatening.

‘He mumbled and said it was ‘their fault’,’ the prosecutor said, adding that he used an extremely offensive swear word, and had clenched fists.

He was searched and taken into custody, but gave a ‘no comment’ interview to police.

The court heard he had no relevant convictions, but had appeared before the courts in 2021 and 2017 for drugs offences.

He was on police bail at the time of this incident due to some sort of dispute with his mother, which has since been dropped.

Chief magistrate Paul Goldspring released heavily tattooed Dorrall on conditional bail and said all sentencing options remained open.

Security at the Houses of Parliament has recently been strengthened with a high new fence 

The case was adjourned for pre-sentence reports.

Sources told this newspaper, which first revealed the remarkable security breach, that the alleged intruder gained access by climbing over the roof of the Parliamentary Education Centre at the southern end of the palace.

Yet neither Scotland Yard nor the Parliamentary authorities announced the security breach publicly or alerted all members and staff to it, raising suspicions that they wanted to avoid the embarrassing publicity.

It came just months after the new fence – branded ‘hideous’ by peers – was put up along the boundary of the parliamentary estate while £10million was spent on a door that did not work.

One insider told this newspaper: ‘After £10m on a door and other works which is still not fully operational, at least £4.5m on a high security fence it is a complete embarrassment that someone can just climb in and get so deep into the site before being stopped by a workman.

‘No wonder it has been kept secret.’

In response to inquiries from this newspaper, a House of Lords spokesman said: ‘We can confirm a member of the public was arrested for trespassing on the Parliamentary Estate on Sunday 30 November.

‘This is being dealt with by the Metropolitan Police. Following the incident security arrangements were urgently reviewed and enhanced measures put in place.’

Asked if members of the Lords were told, the spokesman said: ‘As is normal practice the relevant domestic committees and office holders in the House were informed about the incident.’

A spokesman for the Metropolitan Police confirmed: ‘Police were called at 13:04hrs on Sunday, 30 November to the Palace of Westminster where they arrested an intruder.

‘He did not come into contact with any staff or members of the House.’

It was the latest in a series of major alleged security breaches to hit Parliament.

In November two men were arrested after a phone was planted in the Commons chamber in an apparent attempt to play ‘sex noises’ during Prime Minister’s Questions.

In March a man spent 16 hours perched on a ledge after climbing up the clock tower of Big Ben to unfurl a Palestinian flag.

Four years ago a man scaled the fence near the Carriage Gates entrance to Parliament and got into New Palace Yard, despite security being strengthened after PC Keith Palmer was stabbed to death by terrorist Khalid Masood in 2017.