The festival has barely begun but already light-fingered individuals have been making the most of a town full of distracted campers.

Since Tuesday, there have been three thefts and an assault reported to police, and people are being encouraged to leave any valuables at home.

In the early hours of Wednesday morning, a 19-year-old from Brighton was sleeping on the side of Richfield Avenue waiting to queue for a ticket when he was woken at 12.30am by two men and punched in the face.

Later the same day, between 7.30pm and 8pm, offenders went into a tent and stole a mobile phone, purse and digital camera belonging to an 18-year-old from Sutton in Surrey.

Around the same time, at 7.45pm, three black youths cycled past a 59-year-old man from Gloucestershire on the towpath by Caversham Bridge and made off with his rucksack that was only 10ft away from him.

The bag contained his clothing, ID, financial documents, cash and sunglasses. The offenders are aged between 16 and 18, one had dreadlocks and all were wearing baseball caps.

Between 1am and 5am yesterday, a 19-year-old girl from Caversham had left her bag in her tent while she sat around a campfire. When she returned, the bag, containing money and financial documents, had gone.

John McNicholas, crime reduction adviser for Thames Valley Police, said: “Revellers are urged to only bring valuables they will actually need. If you do bring anything into the site that is valuable, please make sure you use the lockers provided at Rivermead.”