She did it for Macca - now can she do it for Madonna? Fiona Shackleton, the divorce lawyer who ensured that Sir Paul McCartney retained all but £24.3 million of his £825 million fortune, has been lined up by the pop star.

Madonna, whose fortune is estimated to be worth £300 million, is understood to be seeking legal advice on a possible divorce from her husband of seven years, the film director Guy Ritchie. Ms Shackleton, 52, is the lawyer of choice for the rich and famous after what was regarded as the spectacularly well-handled split of Sir Paul from Heather Mills, who was rumoured to be pushing for £80 million.

Dubbed the “steel magnolia” for her tough but pragmatic negotiation tactics, Ms Shackleton instructed the top divorce silk, Nicholas Mostyn, QC. They secured such a successful result that Ms Mills emptied a jug of water over Ms Shackleton’s head after hearing the judge’s ruling.

Ms Shackleton also acted for the Prince of Wales in his divorce.

Yesterday Madonna’s spokesman refused to comment on the claims. But one lawyer told The Times that the word in legal circles was that Madonna had gone to Ms Shackleton after making an approach to another firm. Guy Ritchie is thought to have had dealings with a lesser-known Mayfair law firm, Forsters.

There has been speculation for some time over the marriage of Madonna, 49, and Ritchie, 39. It is thought that the couple did not have a prenuptial agreement, which means that the starting point for any settlement would be a 50-50 split.