The spectacular success of 52-year-old Fiona “Steel Magnolia” Shackleton as Britain’s most celebrated family lawyer — charging her rich and famous clients £500 an hour for her services — seems to suggest that you do not need a good or even passable law degree in order to get to the top of some branches of the legal profession.

With a humble third-class law degree from Exeter University in 1980, Shackleton (who is also a trained cordon bleu chef), could not have been more successful if she had received a glittering double first from Oxford or Cambridge universities. She has represented the Prince of Wales, Prince Andrew, Sir Paul McCartney and Rick Stein, the celebrity chef, in their highly publicised divorce cases, while also advising the princes William and Harry.

Exeter University is not in the same league as Oxford and Cambridge, but it has a reputation today for being the place to go for many of the children from privileged families who are accustomed to getting their offspring into Oxbridge without much effort. Because of fierce competition it is to Exeter to which they turn instead.

A former partner of Farrer & Co — the Queen’s law firm — Shackleton was educated at Benenden, the exclusive girls’ school in Kent (where the Princess Royal was educated), and is now a partner with Payne Hicks Beach.

Graham Zellick, Cambridge graduate and law professor — who was a law school dean for 20 years and is a barrister and master of the bench at Middle Temple as well as chairman of the Criminal Cases Review Commission — says that he is not amazed that a law graduate with only a third-class degree should get to the top of the profession. “It doesn’t surprise me. There are all sorts of reasons why people don’t do well at university or in exams. There are different kinds of intelligence, many of which aren’t assessed in exams. Some legal practice requires high intellectual ability. Family law does not.”

But a 32-year-old conveyancing lawyer, Simon Nosworthy, a law graduate of York University and partner of Cree Godfrey & Wood in North London, is very surprised that a third-class degree is anything other than “pretty hopeless nowadays” because “even getting a 2:2 leaves you in a difficult position. We live in a tick-box world and without a 2:1 you are not going to be ticking many boxes.”

Clive Thorne, a Cambridge law graduate and an intellectual copyright lawyer and partner with the City firm Arnold Porter, says: “As in any profession, luck is important, being in the right place at the right time — same as being an actor or a journalist for that matter. Being at Farrer & Co cannot be a bad break.”

Warren Roiter, a law graduate of Queen Mary London and partner of Roiter Zucker at Swiss Cottage in North London, believes that good degrees are not the whole story, because he says that his firm will “employ anyone who can provide the quality of advice and level of service needed in these challenging times, with a good degree or not”.

As a role model for thirds, Fiona Shackleton is up there with the best. Not that she is a role model for Exeter University thirds any longer, according to Professor John Usher, head of the school of law at Exeter, because he reckons that “these days” the school “awards hardly any thirds and very few 2:2s”.

This raises the question of declining academic standards making it much easier these days to achieve higher and to avoid lower degrees. One legal academic suggests: “It’s pretty difficult to get anything less than a 2:1 even at the best universities.” By the same token, it may also be impossible to get a third any longer.

As for whether Professor Usher was surprised that Fiona Shackleton has gone so far with only a third, he replied: “I am certainly very impressed.” Nor, he adds, is he of “ of the opinion that standards are declining”.

Times Recommends

• City law firms prepare for painful year ahead
• Welcome to 2009: the year of the regulator
• Thacher Proffitt is latest US legal casualty