A secret 19th-century tunnel buried beneath the Surrey Hills has reopened after 50 years, lifting the lid on a hidden world of Victorian engineering, social hierarchy — and a surprising link to Ada Lovelace.

The 120-metre passage at Horsley Towers in East Horsley, now part of the De Vere Horsley Estate, was built in the 1800s as a discreet service route. Its purpose reflects a very Victorian division of life, keeping the “upstairs” and “downstairs” worlds firmly apart. As estate staff once described it, it was designed so “servants could move unseen, carrying goods without crossing the formal life of the house above”.

The tunnel’s reopening follows a £1.3 million refurbishment project and more than half a century of closure. Visitors can now once again walk its length, with the restored space described as “a hidden chapter of British history brought back into the spotlight”.

What has drawn particular interest is its connection to Ada Lovelace — mathematician and widely regarded as the world’s first computer programmer. The only legitimate child of Lord Byron, Lovelace lived at Horsley Towers for part of her life. It is believed she experienced agoraphobia, and local accounts suggest the tunnel may have allowed her to move “with greater confidence and privacy across the estate”, avoiding more exposed areas of the grounds.

While documentation is limited, historians say it offers “a rare glimpse into both the social history and private lives of those who lived there”.

The estate later became home to aviation pioneer Thomas Sopwith, founder of the Sopwith Aviation Company.

General manager Michael Micallef said: “Reopening this tunnel is a way to celebrate both the rich history of De Vere Horsley Estate and the remarkable legacy of Ada Lovelace. For generations, the tunnel has been a secret passage full of stories, from its origins serving the estate, to the memories of locals growing up with it and we are delighted to now share this hidden part of our heritage with the wider community once again.”