Grade I listed Seaton Delaval Hall in Northumberland will be redeveloped and reopened as a visitor attraction following a fundraising campaign led by the National Trust (NT).

Built between 1718 and 1731 by Sir John Vanbrugh, architect of Blenheim Palace and Castle Howard, the hall - near Blyth in the south east of the county - is widely regarded to be the finest work of the English Baroque and one of the most important historic houses in Britain. The hall, its gardens and much of the contents of Seaton Delaval were accepted by the Government in lieu of inheritance tax and gifted to the National Trust through the Acceptance in Lieu (AIL) scheme following the death of the previous owners.

In addition to £6.9m pledged by the NT from its own resources, more than £3m of funding came from individual donations, charitable trusts and private companies. The NT plans to open Seaton Delaval Hall to the public in spring 2010. Plans for its development include an arts centre in the Main Hall, providing a flexible space for exhibitions and performance; giving individuals and groups the chance to bid to take over the Salon for a temporary exhibit or activity; the restoration of the Walled Kitchen Garden through offering gardening plots to schools, other community groups and visitors; and giving the public the opportunity of shaping the Trust's plans for the East and West Wings of the hall.

Fiona Reynolds, director general of the National Trust, said: "This is a wonderful Christmas present for the nation. It has been an incredible journey and we have been thrilled by the goodwill and support we've received from so many people. "From the start of the campaign we've worked together with the public - and especially the local community - to shape Seaton Delaval Hall's future and decide how the building, gardens and grounds can best be used for the benefit of everyone."

She added: "Over 100,000 people took part in the biggest public consultation in the National Trust's history and they showed us overwhelmingly that they wanted the National Trust to secure Seaton Delaval Hall's future." Jonathan Scott, chair of the AIL Panel commented, "The importance of Seaton Delaval Hall was immediately apparent when MLA's AIL Panel visited the property in the summer of 2008.

"This is a major heritage attraction for the North-East and will be a significant boost to the tourism of the area. For the first time, all of the property will be accessible to visitors."