RARE species are now populating Hindhead’s former bottleneck, thanks to the £371million project to build the A3 Tunnel that joined two commons to create a top wildlife site.

Representatives from Highways England and Natural England joined lead National Trust Surrey Hills ranger Matt Cusack at the Devil’s Punch Bowl to celebrate the sixth anniversary of their successful partnership project, on Tuesday.

Six years on, the Site of Special Scientific Interest has been granted “favourable status” by Natural England and seen the return of rare breeding birds, such as the Dartford warbler, woodlark and nightjar, and a sighting of the nationally scarce heath tiger beetle.

The National Trust is now planning to introduce more endangered species, notably the sand lizard and the Silver Blue Studded Butterfly.

“Matt and his team have done a fantastic job at taking on board actions needed to achieve favourable status,” Natural England conservation adviser Graham Steven said.

“Since the commons were joined, it is less of a barrier to wildlife . Many species found it difficult to get past the dense woodland on either side of the old A3. This is now one of the largest SSSIs in Surrey.”

Highways England’s senior environmental adviser Henry Penner, who has been involved with the project since the 1980s, added:

“I’m thrilled to have been working on this. It was very forward thinking, considering the cost. The tunnel is the longest of its type in the UK and the old A3 was filled in using sandstone excavated from the tunnel and a mix of seeds to match the surrounding environment.”

Managing the area to encourage wildlife is a challenge, as the SSSI is one of the highest points in southern England and includes a mosaic of habitats including upland and lowland heath, bog, streams, ancient woodland and free-draining sandy soil. The transformed landscape now attracts many more visitors.

There has been a 20 per cent increase in numbers from 2011 to 700,000 per year.

Earlier this month, the trust got full planning consent for a £775,000 project for major improvements to the cafe and car park to cope with the extra numbers.Matt and his team have created new paths to enable visitors to enjoy the landscape while avoiding wildlife disturbance in sensitive heathland areas, and have opened up new views from the cafe, including the Gibbet Hill cross.

Matt said: “I am thrilled we’ve achieved favourable status for Hindhead and the Punch Bowl during my watch. The removal of the A3 was a major milestone, enabling us to thin trees and transform the site into a swathe of heathland.

“Heather mowing, the introduction of woodlark nesting areas, grazing by Highland cattle and ponies, and scrub management conducted under a higher level stewardship scheme has transformed it.

“This couldn’t have been achieved without the support of my team and Hindhead’s dedicated local volunteers.”