A JMW Turner painting of Chepstow Castle overlooking the River Wye is to be sold at auction where it has an estimate of £30,000 to £50,000.

The British artist was 19-years-old when he created the watercolour painting, which has been kept in a private family collection in London since 1956.

The artwork is signed “Turner” and dated 1794, with the attribution confirmed by leading Turner scholar Andrew Wilton, Cheffins auctioneers said.

It is to be sold at Cheffins in Cambridge as part of The Fine Sale on March 22.

Patricia Cross, an Associate at Cheffins, said: “This painting is an important record of Turner’s early style which was developing at a fast pace at this time of his life.

“His use of colour and perspective and extraordinary attention to detail are characteristic of his work in the early 1790s and can be seen in various other watercolours of the period.

“Given its large scale and highly finished composition, it is likely that this would have been painted as a presentation piece for an important patron, such as Dr Thomas Monro, in whose collection this watercolour was found in 1833.

“The present view would have been created during one of Turner’s first tours throughout England and Wales as a professional artist.

“Turner is considered one of the greatest landscape painters in the world, and this is an important collectors’ piece, offering a glimpse into his painting style in the early part of his career.”

JMW Turner died in 1851 aged 76.

The painting, which is being offered on the open market for the first time in nearly 100 years, is one of only two Turner paintings of this view of Chepstow Castle and bridge in Monmouthshire known to be in existence.

The other is currently held in the Courtauld Institute of Art.

The painting depicts Chepstow Castle overlooking the River Wye, showing the view from downstream of a wooden bridge, complete with a boat in the foreground and the castle, alongside a series of cottages.

The version held at the Courtauld Institute is undated, less finished and smaller than the painting to be offered by Cheffins, according to the auctioneers.

Differences can be observed in the arrangement of the boats, the detailing of the town and castle and the position of the figures on the bridge.

Cheffins described the painting as “in immaculate condition”.