The cottage is the last remaining in public ownership in NI

The programme, which aims to save a heritage property for the nation, returns later this summer.

Last year, the historic home of the Staples family, near Cookstown, County Tyrone was pipped to the multi-million pound prize by Manchester's Victoria Baths.

Leading the province's challenge is the Lock Keeper's cottage at Newforge, Belfast, which is the last remaining one in public ownership on the famous Lagan Navigation canal network.

The derelict cottage played a vital role in a water transport system which served Northern Ireland.

Built between 1827 and 1934, the vernacular two-storey house with four rooms is testimony to a way of life that is almost forgotten.

In 1954, the Lagan Navigation Company was dissolved, unable to compete with modern transport.

The lock-keeper bought the cottage and stayed there until his death, willing it to one of his daughters who in turn sold it to the council so that it would stay in public hands.

Armagh Gaol is one of NI's three entries in the competition

However, Northern Ireland's oldest prison, Armagh gaol, will provide stiff competition.

Built between 1780 and 1852, the prison buildings span the history of incarceration in Ireland from the mid 18th century to the late 20th century.

In 1765, the Archbishop of the Church of Ireland was appointed to Armagh and set about improving the city with buildings designed by Northern Ireland's finest architects of the time - Francis Cooley and William Murray.

However, in the mid-1800s overcrowding became a problem with up to 10 prisoners sharing a cell. In 1920, the gaol was used for women and by the 1950s it housed no more than 12 female prisoners at a time.

Finally, with the onset of political unrest, Armagh Gaol became a place for holding female political prisoners.

In 1986 the prison closed and has lain empty ever since.

Londonderry's Playhouse, which stands taller than most of the city's buildings is the province's final entry.

Londonderry's Playhouse enjoys stong community support

Set on one of the oldest sites in Derry, nestled against the city walls, the Playhouse is situated in the former St Mary and St Joseph's school buildings, part of a complex originally owned by the Sisters of Mercy.

Built between 1887 and 1911, the building tells the story of the first convent to be set up in Northern Ireland after the reformation.

Schooling on the site came to an end in 1981. Eleven years later, in 1992, the playhouse was established and has grown into one of Northern Ireland's most diverse and busiest arts centre with strong community support.

Griff Rhys Jones returns to launch this year's campaign and give details of the 21 historic buildings across the UK that viewers will be able to vote for.