A mnage trois by mutual consent

EVEN for the excesses of 18th Century English aristocracy this was a strange collision of lives.

Lady Elizabeth Foster was a member of the eccentric Hervey family, who married young and repented in haste. Georgiana was the daughter of an Earl, who became mistress of one of the greatest houses in the land.

The two were friends for nearly 30 years and the bond between them was strong enough to sustain their shared love for one man - Georgiana's husband the Fifth Duke of Devonshire.

This mnage trois, played against bloody episodes in European history, didn't exactly shake the be-wigged and powdered foundations of Georgian society, but unless what passed between the two women had sapphic undertones, it was indeed a relationship of extraordinary breadth.

Amanda Foreman's best-selling Georgiana, Duchess of Devonshire first drew public attention to the parallels between her subject and Diana, Princess of Wales.

Both Spencers, both beautiful and married to older, excessively wealthy husbands... each had to endure their husband taking a mistress.

For Diana it was to have tragic consequences. For Georgiana, far from being a rival, "Bess" Foster was to prove an inseperable companion. Three people may have been in the Devonshire marriage, but it was wholly by mutual consent.

Here, Chapman has collaborated with Jane Dover, the great-great-great-grandaughter of Elizabeth, who allowed unlimited access to family archives, journals and unpublished letters.

The result is a much weightier and authorative version of the friendship first offered by Foreman.

The pair met while taking the waters at Bath, in 1782. "For Bess to be taken up by the Devonshires at such a moment in her life was little short of a miracle," suggests Chapman.

"The Devonshires were both seeking diversion and it fell on Bess to supply it.

"She cannot have foreseen that a summer spent in their company would lead to friendship lasting until Georgiana's death, or that she should fall in love with the Duke."

Bess and the Duke may have become lovers within weeks of their meeting, but it is more likely this happened when she returned from her Grand Tour in 1784 and conceived a child by him.

Georgiana's initial thoughts on the friendship may have been that Bess aroused the Duke and increased his potency, thus enhancing her own chances of producing an heir."

Early in 1784 she wrote: "I am equally loved by both and (hope) that we three may pass our lives in making one another happy."

When Geogiana eventually produced the longed-for heir and then, an illegitimate daughter by the politician Charles Grey, it was Elizabeth - now with two children of her own by the Duke - who accompanied her in long years of exile.

Seven months after Georgiana's death in 1809, Elizabeth married the Duke and so succeeded her greatest friend as Duchess of Devonshire, but it was to prove a short-lived match, for within two years, he too was dead.

Here is a true story that has waited long in the telling and Chapman does it wonderfully well.

David Chapman