A UNIQUE Grade II listed townhouse with a grisly past is on the market for nearly £800,000.

The original flat roof of the Old Monmouth Gaol Gatehouse on the town's Hereford Road was where condemned prisoners were hanged, in full view of thousands of ghoulish spectators sitting on the bank at what became Monmouth School for Girls.

Opposite the entrance to the newly co-ed Haberdashers' Monmouth School, who currently own the historic building, the house dates back 235 years to 1790 when the county gaol was built by architect William Blackburn.

In 1850, two Irishmen Maurice Murphy, 21, and Patrick Sullivan, 23, were publicly executed there for the murder of an elderly woman in Newport, reportedly watched by a crowd of about 3,000, of whom "four-fifths were estimated to be of the softer sex".

The last execution took place there in 1859, when Matthew Francis, a 25-year-old tailor and haulier from Newport, paid with his life for the murder of his wife Sarah.

Thankfully, the town was spared the hanging, drawing and quartering of Newport Chartist riot leaders John Frost, Zephaniah Williams, and William Jones – convicted of treason at Monmouth's Shire Hall in 1840 – when Prime Minister Lord Melbourne commuted the sentence to transportation to Tasmania.

Designed as a ”reformed gaol” following the principles of the first prison reformer John Howard, the prison lasted until 1869 when it closed and prisoners were transferred to the new jail in Usk.

Made a Grade II listed building in 1974, the Gatehouse has been a home since the rest of the prison was demolished in 1884.

David James Esatate Agents are marketing the house as: "A unique opportunity to purchase a historic Grade II listed property built of local stone with a wealth of character features.

"The Old Gaol offers flexible accommodation, including five bedrooms, four reception rooms and a ground floor ensuite bedroom/study.

"The property can be enjoyed as it is but allows scope for further modernisation. Outside is extensive parking, six garages and level gardens with a large terrace ideal for entertaining.

"The Old Gaol dates from 1790 and was designed by architect William Blackburn.

"It served as the county jail of Monmouthshire until 1869. In 1884 most of the building was demolished leaving the Grade II listed Gatehouse largely as it is now, as an impressive, detached residence."

Entrance is via a solid front door to a reception hall, featuring an oak door with a large lock and smaller door, and a historic stained-glass window showing The Old Gaol.

A utility room, cloakroom with an original cell door, and a kitchen with a “Stoves” gas range oven are off the hall, while the main sitting room looks out onto the rear garden with French doors to the terrace.

Further living areas include a dining room, a second sitting room, and a family room with a stone fireplace.

Upstairs, bedrooms have sash windows offering garden and countryside views. Bathroom facilities include both a shower room and family bathroom.

Offers over £799,950 are invited from the agents.