The Exiled Collector by Anne Sebba

Pursuit of beauty by remote control

We are a society addicted to home improvements. With a sheet of MDF and a few relics rescued from the back of the garage, we have all been encouraged to believe by Laurence Llewelyn-Bowen and his acolytes that we can create our own Petit Trianon in Penge. William Bankes worked on a larger scale, but essentially shared the same dream.

Even before the death at 21 in 1806 of his elder brother, Henry, Bankes had been planning a makeover for Kingston Lacy, the family seat in Dorset. But as son and heir to the estate - as well as to Soughton Hall, a slice of north Wales owned by a great-uncle - he quickly developed his own grand designs for changing both rooms and façades.

However, his pursuit of an eclectic artistic and architectural vision was interrupted by a moment of madness with a guardsman in some bushes in London's Green Park in 1841. Gay sex at that time carried the death penalty and Bankes was forced to flee into exile, pursued by a vindictive (Tory) government which declared him an outlaw and forced him to sign over his properties to a younger brother to prevent them from being seized by the state. For the last 15 years of his life, living in Venice, Bankes had to complete the rebuilding of Kingston Lacy by remote control, never seeing with his own eyes the achievement of his vision.

Anne Sebba tells this tale of talent and tragedy with great aplomb, producing in the process a wonderful hybrid of a book that is part biography, part tear-jerker, part lesson in art and architectural history, and part guide book to what is now one of the finest properties in the National Trust's portfolio. She even manages to weave in some insights into the psychological make-up of the great collector of artefacts, contrasting Bankes's need for "emotional support in an unfriendly world" with the motivation of history's other hoarders.

She is helped enormously by her subject's knack for rubbing shoulders with figures who have enjoyed a more enduring fame. Looming largest in Bankes's life was Lord Byron. They were close as students at Cambridge where their relationship caused such jealousy among Byron's circle that they accused Bankes of "attaching himself to Byron's coronet". There was certainly an ongoing rivalry between the two men, one flamboyant, the other arrogant, but both single-minded. Yet there was also an enduring friendship and respect. They both proposed simultaneously to the same woman - Annabella Milbanke. She said yes - disastrously - to Byron and no to Bankes, who she rightly suspected as being half-hearted in his suit.

Sebba shows her mettle as a biographer (her previous subjects have included Enid Bagnold, Laura Ashley and Mother Teresa) by her handling of Bankes's sexuality. It would have been all too easy to make him a gay martyr and use the appalling 19th-century prejudice he suffered as a stick to beat those who today still believe homophobia has any place in a civilised society. But that would have unbalanced the text. Equally, she could have indulged the prurience of contemporary readers with speculation about what exactly went on in the bushes in Green Park - or in the toilets behind Saint Margaret's Church, Westminster, where in 1833 Bankes was arrested with another soldier, but on that occasion eventually acquitted.

Instead, Sebba conveys the facts, the context and the consequences with a benign detachment. Bankes, she shows, was bisexual. As well as his failed proposal to Annabella, he had a notorious affair with the Countess of Buckinghamshire. And Sebba is not afraid to explore ideas that for some might seem politically incorrect - such as the suggestion that an artistic temperament and sexual orientation could be linked.

But this is absolutely not a psychologically intense portrait. Rather it focuses on the wonderful detail of Bankes's life - his youthful "shopping sprees" in Spain buying Zurbarans, Murillos and Velasquezes for what became the ornate Spanish Picture Room at Kingston Lacy; his pioneering role in 19th-century Egyptology and his jaunts around the Near East where he clashed with another formidable traveller, Lady Hester Stanhope; and his often comical attempts as an MP to make a name for himself as an orator on the floor of the Commons.

His monument, however, is Kingston Lacy, preserved in aspic by successive generations of the Bankes family before being handed with its contents to the National Trust in 1981. The story of his work with Charles Barry, architect of the Houses of Parliament, to revive earlier plans that Inigo Jones had drawn up for the property, is fascinating. In later years he would send off from Venice plans and drawings for a house he hadn't seen in years (and didn't own) but over which he insisted on maintaining the most exacting control.

You end up yearning for there to be a happy ending. There were, Sebba recounts, local stories that he used to sail into Studland Bay at night and wander round his house, leaving before morning, but try as she might she cannot make them stand up to historical scrutiny. Perhaps we just have to let our imagination run away with us. That was after all the genius of William Bankes.