Under the cover of darkness, the Sheriff of Oxford, council staff, and volunteers on quad bikes could be seen rounding up cattle on Port Meadow yesterday.

The dawn raid may have looked an odd sight but it was actually a medieval custom where animals are driven off the meadow and into a pound.

As only the Freeman of Oxford and the Wolvercote Commoners are allowed to graze livestock for free, the ceremony aims to track down cattle that should not be there.

The date of the round-up is kept top secret, so that owners without grazing rights cannot remove their animals at the last minute and escape a fine.

Sheriff of Oxford Susanna Pressel said: "It was great fun.

"I am particularly pleased to have done this as Port Meadow is in my ward and I have lived near the meadow for most of my life.

"It is such a special and beautiful place."

Anthony Roberts, head of the city council's Countryside Service, which is responsible for rounding up the cattle, said they caught about 250 cattle.

He said: "Owners then come along and say how many animals they have got, and pay a small toll.

"It went pretty smoothly - all but about five of them were caught."

He said city council staff, Ms Pressel and other volunteers teamed up for the ancient tradition, adding that there were no illegal cattle on the meadow.

Sheriffs of Oxford have used a variety of transport methods when conducting the annual round-up in the past - some have ridden horses, others have walked or driven in vehicles.

One, a former Air Vice-Marshal, even commandeered a helicopter.