Among the historic buildings in The Railway Works, Historic England’s archive is a bit of a modern anomaly. A large grey shed, it’s not much to look at.

But inside are more than 12 million photographs in the nation's biggest collection of historic images.

Visitors on Saturday will be able to take a tour of Historic England’s headquarters in the Engine House and also its huge archive.

Inspired by the Astounding Inventions theme for this year’s Heritage Open Days,  displays at the Engine House will be all about photography, showcasing fascinating examples past and present from the millions of items in the Archive’s collections.

Visitors will h be able to see original 19th-century cameras, discover historical and aerial photographs from the archive, and learn how the collection is kept safe and preserved.

Aseye Negedu, engagement and volunteering Officer at Historic England, said: “We are very excited to take part in Heritage Open Days this year. Is there a more astounding invention than photography? We are fortunate to have so many examples which tell its story from its earliest days to the present. If you’ve ever wondered where our love affair with taking pictures started, this is the event for you.”

Wendy, a volunteer at the Archive, said: “I have always loved photography, especially older images. Working at the Archive gives me the chance to compare them with the present day to see how buildings have survived and evolved to serve new purposes. Several have sadly disappeared, but so many are still around, hidden by new frontages and renovation”.

One last thing. Bring a coat, the archive is kept at a constant, chilly six degrees Celsius to preserve the photographs.

The Engine House is open from 10am to 3pm on Saturday.