A man who went into a rarely used spare room in his mother's home was shocked to discover that 5,000 wasps had made a giant nest in the bed.

The nest, 3ft wide x 1.5ft deep, was still expanding and the insects had chewed through the mattress and pillows to build it.

When pest controller John Birkett was called to the scene he realised it had been growing for several months. His client, who lives alone in the five-bedroom house in Winchester, Hampshire, had not been in the spare bedroom for months. When her son opened the door and discovered the nest in the single bed he realised a window had been left open the whole time.

Birkett, of Longwood Services, said: "We got a call as we normally do … but a bedroom – I thought that was unusual. I opened the door and I just couldn't believe it. The pillow was covered in this 3ft wasps' nest and the workers were still busy building the nest.

"In 45 years I have never seen anything like it. There must have been 5,000 wasps. It's amazing that the woman didn't realise she was living with them.

"I got dressed up like a spaceman and tried to destroy as many as I could with the workers flying around the room. In that nest there must have been up to 700 queen wasps."

He said the only nest he had previously found in a room was about the size of a tennis ball.

Birkett finally managed to clear the area using a spray to kill the wasps. He was even able to rescue the beloved blanket on the bed.

Though he got the job done, Birkett was saddened at the death of so many wasps. "It was a work of art and they had worked so hard, but she looked at it and said, 'No, no, no - you've got to get rid of it.' If they did that in three-and-a-half months, that's amazing, isn't it? They're just little things."