A Napoleonic seafort and Martello tower in Inishowen, Co Donegal, which incorporates a seafood restaurant, bars, function room and six bedrooms, is being offered for sale. The property carries a guide price of between £500,000 and £550,000.

The historic Greencastle Fort represents a rare investment opportunity and will be sold at auction by Ganly Walters on September 14th and offers.

The property was formerly a hotel in the 1920s and is being sold by James and Jean McGonagle, who are retiring from the business. Two years ago, offers in excess of £900,000 were sought for the 19th century fort by the same owners.

The property lies at the entrance to Lough Foyle and the fort and Martello tower were strategically placed here to protect the city of Derry from a French invasion force under Napoleon. The main building, set in five acres, is fronted by a spacious car-park overlooked by the ruins of Northburg Castle. Entry through the front tower leads to the reception area and then to the bars, restaurant and bedrooms.

The Master Gunners Bar looks out on a courtyard and beer garden, formerly the parade ground of the original fort. It seats 75 with the outer lounge accommodating an additional 30.

A back lobby, which seats 12, connects to the residents lounge, formerly the officers mess.

Upstairs is the Cannons Restaurant, which enjoys magnificent sea views and is a popular venue for wedding receptions and dinner functions.

The Martello tower has three levels and is currently unused.