Masked men who scaled the Guildhall and erected a pirate flag at the top said they did it to "cheer up the city".

As reported in the Mail, the skull and crossbones was discovered flying high above Hull when city council staff returned to work after the weekend.

Now, two dads in their 30s have owned up to the stunt.

The culprits, who go under than names Squirell911 and Branded, told the Mail they scaled the 70ft building in Alfred Gelder Street, city centre, in the early hours of Sunday morning, via scaffolding.

They then hoisted the Jolly Roger and had a picnic on the roof.

Squirrell911, a 36-year-old married Hull man, said: "I was driving past and I noticed some scaffolding going up round the side of the Guildhall for some work to be done.

"I also saw a forlorn flagpole on the roof that just needed a flag to adorn it, so I hatched a plan."

Both men have rock climbing experience and said it was relatively easy to carry off the practical joke. They scaled the building without the aid of any equipment.

Squirrell911 said: "When we got to the top, we just watched the world go by. We had sandwiches and a flask of tea and then put the flag up.

"It was not political in any way – the pirate flag was just the first one that came to mind."

The friends took pictures of their stunt and posted them on the website www.28dayslater.co.uk

They use the site to show off their "urban explorations", which involve entering derelict buildings and taking photographs of the inside.

Squirrell911 said: "I just thought it would get the people of Hull talking and cheer them up on Monday morning. I also thought it was a chance to get some great photos of the city at night."

Squirrell911 said he had been into the former Hovis factory, LA's nightclub and the Lord Line building on St Andrew's Dock, among others in the city.

The flag stunt was a first for the duo though.

Squirrell911 said: "We won't be going back up the Guildhall because we have done it now and we don't want to rub their noses in it.

"But, as for other pirates flags popping up around the city? Never say never."

Baffled council bosses took the prank in good humour.

They did, however, issue a warning about the potential risks involved in climbing up the scaffolding.

But Squirrell911 insisted they were careful.

He said: "We are not kids and we have experience of climbing.

"We would not want an ambulance to have to be called out because of us, so we never do anything we cannot do safely."

A spokeswoman for Hull City Council said the matter would not be reported to police.