Missing Irish teenager Patrick Halpin / Regina Halpin

It is believed to be that of 18-year-old Patrick Halpin, who disappeared after a night out in London's West End

Police say that they believe a body found near Leicester Square in London is that of missing Irish teenager Patrick Halpin.

The 18-year-old, who was on a trip with Dublin City University’s Drama Society, was last seen shortly after midnight on Wednesday when he left the Zoo Bar in Bear Street, off Leicester Square.

Scotland Yard said they discovered a body at around 7.50pm yesterday in an enclosed space off Leicester Square, close to both the bar and a Burger King restaurant.

"Though formal identification has not taken place, we believe that the deceased is Patrick Halpin, 18, from Ireland," the Metropolitan Police Service said in a statement on Friday.

According to reports in the London Evening Standard, the body was found on top of a four-storey building on Bear Street.

CCTV footage shows him climbing external stairs leading up to the roof of the nightclub and neighbouring buildings.

A nearby worker who asked not to be named told the Standard: “Police told us there was CCTV of him going up a staircase and we were told that’s how he had got up to the roof.

The tragic discovery comes just hours after Patrick's family were mistakenly told that he had been found when Gatwick Airport reported he had checked in for his flight home to Ireland.

The tickets had been booked as a group and check-in staff had failed to note the teenager’s absence.

Patrick’s father, Paddy, and 22-year-old sister Regina travelled to the capital on Thursday to help with the search.

Regina had earlier issued a social media campaign to help trace her younger brother. In a Facebook appeal she wrote: “(Patrick) was in London on a trip this week and went missing from a nightclub last night and hasn't been seen since.

"He was in The Zoo nightclub just off Leicester Square and left to go to Burger King but did not return home. He should have been staying in the Astor Museum Hostel, Bloomsbury, London."

A later post appealed for help in carrying out a search: "Hey everybody, this is Regina's friend posting on behalf of the family. We really appreciate all your messages and offers of support, we plan to carry out a search tonight if anyone in the London area is available."