Slides of Charles Rennie Mackintosh masterpiece found on eBay

The pictures were taken by a US architect in the 1970s

Holiday snaps discovered on eBay have given conservation experts new insight into the history of Charles Rennie Mackintosh's domestic masterpiece.

The images of Hill House in Helensburgh, Argyll and Bute, taken in the 1970s, include views of the interior and exterior of the property.

Taylah Egbers stumbled across the 30 slides while doing research online.

The pictures, bought from a seller in the US, were taken by an architect on a visit to Scotland.

The Hill House was designed and built by Mackintosh for publisher Walter Blackie between 1902 and 1904

Conservationists said the images will help them create a visual timeline of decorative alterations made by previous owners, such as the ceiling in the drawing room, which was plum-coloured for several decades.

Ms Egbers, visitor services supervisor at the National Trust for Scotland property, said: "I stumbled across the slides online and thought 'those are brilliant'.

"From the advert I saw they were not really images that I'd seen before and I thought those will be great for the house to have and also for the conservation project."

The seller had bought the slides from an architect's estate sale.

His wife had told the seller that in the 1970s her husband, who enjoyed photography, spent lots of time travelling around famous places, including Hill House.

The slides show the fire in the drawing room was still in use and the ceiling was a dark plum colour

Ms Egbers added: "We are so lucky he took the photos. It's not very often that you get a set of 30 slides and it's nice because they are so personal, you do get a completely different view of the property than you would if it had been a professional, because they are just somebody's holiday snaps of the property.

Ms Egberts said it was "very exciting" to find the slides, which were bought for around £30 in the eBay sale.

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The Hill House was designed and built by Mackintosh for publisher Walter Blackie between 1902 and 1904.

It is the famous architect's most complete example of a domestic home, with Mackintosh having had a hand in the design of every aspect of the building and its fittings.

The slides show how one alteration brought in by the Blackie family in 1912 was still in place in the mid-1970s.

In 1912 the Blackie family asked Mackintosh to return to the property to alter the drawing room ceiling from white to dark plum.

It remained that colour until NTS took over the care of the property in 1982 and restored the rooms to how they looked in 1904.

Ms Egbers said the photos showed that fireplaces in the house were still being used.

She said: "I thought it was quite beautiful to see the drawing room with the dark ceiling, which is also quite unusual to see, along with the fireplace being on.

"I thought that was really, really interesting, I'd not seen a photo with the fireplace on before so that was my favourite one."

The house was sold to Thomas Campbell Lawson in 1953 and was then cared for by the Royal Incorporation of Architects in Scotland from 1971 until NTS took it over.

There are also slides of rooms such as the white bedroom, showing how little it has changed over the years, the library and hallway as well as several exterior shots.

Ms Egbers said the slides will be scanned and uploaded to the archive to help piece together more about the story of the house.

The house is currently protected by a giant "box" built to protect its saturated walls from further damage from the elements.