When Iona Dudley-Ward began to strip off in a shop window, some passers-by thought she had simply got lost on the way to the changing rooms.

Nonchalantly peeling off her clothes down to her underwear, she tried on several outfits, checking each in the mirror as if oblivious to her mistake.

Onlookers were alternately amused, shocked and puzzled by the events taking place in the window of Oxfam in North Street, Brighton, on a busy afternoon.

It even drew the attention of three policemen after a call from a concerned shopper.

They did not realise Iona, 20, a dance and visual arts student, was taking part in Brighton Festival's window-dressing competition.

Her antics won the first prize of a theatre weekend in Paris.

Iona, of Buckingham Place, Brighton, who is in her second year at Brighton University, said: "I was trying to ignore people passing by so a lot of people thought I didn't realise I was in the window.

"I had people knocking on the glass saying, 'Dear, we can see you.' I just carried on.

"I was so focused it took the police quite a few attempts before I realised they were there."

The confused officers even offered their helmets to cover her modesty.

Iona said: "At first they thought I was a lunatic. They said, 'Do you know you are getting changed in a window?'.

"When I told them it was part of the festival they still didn't believe me and said they would have to ask the manager."

Shop boss Alison Stacey said: "I think they wanted to cart her off at first but once I'd explained they saw the funny side.

"Iona's idea was fantastic. It caused quite a stir."

Thirty shops entered the competition, with second prize going to Rosebys in North Street and third prize awarded to Velvet in Gardner Street. A runner-up prize went to the Alzheimer's Society in Sydney Street.