Despite their best efforts, there is no evidence to work with, says Inspector David George, who is responsible for Safer Neighbourhoods teams in the north of the borough.

CCTV installed in High Street does not point towards the village green and there were no witnesses.

"It was done in the dead of night," explained Mr George. "But we are still investigating."

However, the machines - a digger and a skip loader - are fitted with tracking devices.

The devices are meant to send out a silent signal which can be picked up by the police and homed in on.

But since the theft, which happened overnight between Wednesday, April 16 and Thursday, April 17, the trackers have not given off any signal.

"That could mean they have been cut out and got rid of or the machines are in some sort of box," explained Mr George.

The signal may not be strong enough to penetrate certain materials, for example a shipping container.

The total value of the items is estimated to be around £30,000. Contractors Playdale, of Cumbria, are believed to be claiming from their insurance company.

Mr George said leaving items like this out on site over night during these types of jobs is normal procedure.

The thieves got in to the gated park by cutting through the fence.

It had been hoped that the £50,000 play area would be completed by the Easter holidays but bad weather had already delayed work.

The work is being funded by Hillingdon Council's People’s Choice Award, part of Hillingdon Council’s Feel PROUD campaign.

Once complete, the area will be fitted with swings, springers, new flooring and a climbing frame, amongst other activities.

Anyone with information should call the police on 101.