Wiltshire force expect warm weather to draw large crowds and warns it will take tough stand on drink and drugs

A big police operation involving an unmanned drone, horses and drugs sniffer dogs will be launched at Stonehenge tomorrow as huge crowds descend on the ancient site for the summer solstice.

Because the celebrations fall over the weekend and fine weather is predicted, bigger crowds than usual are expected and Wiltshire police have said they will clamp down heavily on antisocial behaviour.

Restrictions are being placed on the amount of alcohol revellers can bring in and police have said they will not tolerate illegal drug taking or unlawful raves.

The force's no-nonsense approach, after a more relaxed feel in recent years, has raised fears that there could be clashes.

Some peace-loving druids have told the Guardian that they will be staying away because they fear the combination of large crowds - possibly more than 30,000 ‑ and the police's stance could lead to trouble.

Police have played down the idea that the event is the first big test of how police control large crowds since the violent G20 protests. They have denied that the presence of the drone and police horses shows they are taking a "zero-tolerance" approach to the event and say such measures are simply to make sure everyone is safe.

Andy Marsh, assistant chief constable of Wiltshire police, said: "The celebrations will be policed the same as any other public event. We want those attending to have a safe and enjoyable time but within the law.

"This year the event is over a weekend and more people than normal are likely to attend. The public have a right to expect that our planning takes account of the likely increased numbers and also that we will use public resources efficiently making best use of the latest technology."

Marsh warned people not to set up raves or free festivals before or after the solstice. He said the supply and use of illegal drugs greatly increased the danger to everyone and police would deal "firmly but proportionately with any such behaviour".

English Heritage, which manages the site, has stipulated that no more than four cans of beer or a bottle of wine per person will be allowed.

In its guidance English Heritage says: "Illegal drugs are still illegal at Stonehenge as they are anywhere else. The police will be on site during the access period and will take immediate action against anyone flouting the law."