The Lithuanian crane driver would have been the perfect tenant - he was house-proud, scrupulously neat and tidy and an energetic gardener.

In the space of a week he turned a shed at the bottom of an overgrown garden in Banbury, Oxfordshire, into a haven with all the creature comforts of home, including a television and juicer. The only problem was that the shed's owner, Kelly Dudley, had no idea she was sharing her garden with a stranger.

At first Ms Dudley, 25, assumed that the figure in blue overalls had been sent by her landlord to clear the foliage. The truth slowly dawned when she spotted him emerging from the shed on Sunday morning looking as though he had enjoyed a good night's sleep. It turned out that he had.

When she investigated further, she was astonished to discover a single wooden-frame bed, a chest of drawers, a camping stove, pots and pans, crockery and a shaving mirror. The man had even set up a television at the end of the bed, and laid a carpet on the floor.

Ms Dudley, who is on maternity leave with her six-month-old daughter, Chloe, did not know whether to be be amused or frightened.

She later found out that the migrant worker, known only as John, had sought refuge at the bottom of her garden after losing his job and being evicted from his home. He believed that the unlocked brick-built outhouse had been abandoned.

Ms Dudley said: "It beggars belief. The police came and tried to speak to him but all he could say was that his name was John, that he had been there five days and he drove lorries and cranes. I have no idea how he did it. I have been on maternity leave while he has been there, so he moved in right under my nose."

The man had cleared the garden - "without tools" - and planted potted plants in the flower beds. "Once I stopped being scared, I began to feel a bit sorry for him. He is clearly very house-proud. It has been kept very tidy, and is probably nicer than some bedsits you can get in Banbury."

The story has echoes of the writer Alan Bennett's experience with an eccentric old woman, Mary Shepherd, who lived in her van in the driveway of his home in Camden, North London. She was a good deal less amenable than Ms Dudley's "guest" but Bennett was hardly unnerved by her presence, allowing her to stay for 15 years - and he turned the episode into a play.

Ms Dudley said that the Lithuanian had offered to pay her rent and do her gardening if she would allow him to stay, but she was not persuaded to emulate Bennett's generosity. "If I did not have a six-month-old daughter, I might have considered it," she said. "It is a funny story but also very frightening - he could have been anybody."

Banbury has been a centre for migrant workers from Eastern Europe ever since employment agencies began advertising for staff in Polish newspapers in 2004. There are about 6,000 Poles who have settled in the town and many Hungarians and Lithuanians.

Ms Dudley said she contacted the police to tell them that there was a homeless man living in her shed. PC Matt Locke, who answered the call, said that he was as surprised as she had been. "Another police constable and I interviewed the man, who was totally co-operative. The garden, which has access from the road, was very overgrown. He thought the shed had been abandoned, so he moved in. He had even cleaned up the garden. He had not committed any criminal offences but we asked him to move on, which he did, willingly."

Ms Dudley said that the man told the officers that he intended to find a way of returning home to Lithuania. "I don't know if he's coming back but I'd like to speak to him about it if he does," she said.