WHEN pest controller Sean Whelan was called to a break out of wasps at a Southampton pub it didn’t take long to find the source of the problem.

In a corner of the watering hole’s loft he found the biggest wasp nest he had ever seen.

In fact the nest was so large it was the size of a double bed mattress and was home to up to half a million killer wasps.

Built around a chimney stack the six foot by five foot nest was 15 times bigger than a typical one and is thought to be one of the biggest in the UK.

“The wasps were buzzing all over the place. There was enough to kill someone if they weren’t wearing the right clothing,” said Sean, from Whelan Pest Prevention.

“It was without doubt the biggest nest I have ever seen. It was an amazing sight – I couldn’t believe my eyes.”

The pub has not been identified, but its wasps nest has cause a real buzz in the insect world.

Kevin Higgins, from the British Pest Control Association, said: “It’s certainly the biggest I have seen and would be a UK contender.

“I believe the largest ever was found on a farm in New Zealand in 1963 and measured 12 foot long by 5.9 foot diameter.”

Using a telescopic pole, Mr Whelan cracked open the top of the nest and squirted the megacolony with a powerful insecticide.

It is unusual for nests, which are built from wood pulp, to be so big at this time year as the height of the wasp season is still weeks away.

Experts agree the giant nest – one of eight found in the loft – must have been hidden in the pub for at least year to grow so big.

David Baldock, from the Bees, Wasps and Ants Records Society, added: “It’s certainly an enormous nest, but I can’t believe it was a live nest.

“At this time of year queen wasps are just beginning to build their nests but they would be very small nests now.

“I've never seen a nest that size.”