When the National Trust so dramatically bought Tyntesfield last year it promised that the public would be able to enjoy this mighty Victorian Gothic house as soon as possible.

It has been true to its word. The last country house it had acquired, Chastleton in Oxfordshire, was closed for four years before visitors were allowed in. But that was a decade ago, and political and public opinion would no longer tolerate such behaviour – access, quite rightly, is now paramount.

As early as last summer, the first guided parties were admitted, and now, with impressive speed, the Trust has published a beautifully illustrated history of Tyntesfield, offering a tour of the house to those who cannot make the journey to Somerset.

Fertile Fortuneis especially welcome, as booklength studies of individual country houses are uncommon, and books on Victorian houses even rarer. The National Trust is in a uniquely good position to commission and publish such books, so let us hope that more publications on its other houses will follow.

Tyntesfield captured the public’s imagination during the campaign to buy it not because it is a masterpiece or because it contains masterpieces (nor because it was rumoured that Kylie Minogue wanted to buy it, a story not mentioned by Mr Miller), but because it is an enthrallingly complete record of a way of life. Mr Miller’s brisk text, the first account of Tyntesfield to be written with unrestricted access to the family archive, pulls together the many strands of its story. He assembles much significant new information, especially about the furnishings and the creation of the picture collection.

Nonetheless, mysteries remain. Among them is the fundamental question of why William Gibbs should in his seventies have decided to rebuild his comfortable early-Victorian seat on such a Wagnerian scale. He and his family firm had been enormously enriched by the profits made from importing South African guano to use as fertiliser (hence the book’s title), and so perhaps he simply required a building commensurate with his wealth. Yet, as Mr Miller shows, he was a fastidious and retiring man, who was worried that his architect, John Norton, was going to make the house unduly elaborate. Moreover, he did not entail the estate, but left it to his widow absolutely, with instructions that she could sell it if she wished.

His motivations demand the further exploration which Tyntesfield richly merits and has here been so enterprisingly begun.