Barber's book chronicles Charles's successful career at Eton and Oxford, listing a series of girlfriends and detailing at length one well-known adulterous relationship in a chapter entitled "The Sally Ann Lasson Affair".
This concentration on his personal relationships has upset close family members.
Earlier this month, the Palace released a statement detailing the sisters' involvement in the ceremony: In addition to having the support of The Queen, his father The Prince of Wales, and his brother Prince William as Best Man, Prince Harry is also keen to involve his mother's family in his wedding.
All three siblings of Diana, Princess of Wales will be in attendance and Lady Jane Fellowes will give the reading. Markle both feel honoured that Lady Jane will be representing her family and helping to celebrate the memory of the late Princess on the wedding day.
A helicopter, thought to be carrying the newly-weds, was seen leaving the grounds of Althorp yesterday afternoon.
The Earl's third marriage is the latest chapter in his colourful private life, which has seen his previous two marriages end in bitter divorce. In March 2010, Earl Spencer, who has six children by his two former wives, became engaged to Bianca, Lady Eliot, whose husband, Jago, died in the bath after an epileptic fit in 2006.
She remembers Charles as a quiet boy who would sit back and allow his sister to "sparkle" when she returned on holidays from boarding school.