A family battle at the Blackwell's book empire took another surprise turnwhen major shareholder Toby Blackwell's financial advisor threatened to sue him over a £1.1m bill.

The publishing division of the Blackwell business was sold off last month to John Wiley for £550m. Mr Blackwell's cut of the deal was £112m.

But now his friend of 40 years, Christopher Shaw, has claimed Mr Blackwell is refusing to pay him his fee after his company, SP Mergers, arranged the offer.

Mr Shaw said: "It is standard industry practice that the day the client is paid, the advisor is paid. I have a water-tight agreement with Toby but six weeks after the deal I still have not been paid.

"My nose is seriously out of joint."

Corporate finance house SP Mergers has advised Mr Blackwell through the troubled family times of the last eight years, when Toby on one side, and his son Philip, on the other, disagreed over the proposed sale of Blackwell Publishing.

Mr Shaw secured two offers for the business. The first was for £300m cash, the second was for £550m with strings attached.

He says that Mr Blackwell paid up a fee of £1.385m but that he is still owed £1.1m for the John Wiley deal.

He added: "I have telephoned him 11 times and he has always promised to ring back, but never done so."

Mr Blackwell, 78, said: "I have been a little slow, but now it's all in the hands of my very competent solicitors."

The Blackwell business traces its history back to a 12sq ft bookshop opened by Toby's grandfather, Benjamin Blackwell, in 1879 in Broad Street, Oxford.

Julian 'Toby' Blackwell, educated at Winchester College and Trinity College, Oxford, is the son of Sir Basil Blackwell who was born above the original shop and went on to expand the business.

The Blackwell family appeared in the Sunday Times Rich List at number 186 last December with a fortune of £375m but that was before the sale.

Nigel Blackwell, Blackwell Publishing's chairman and largest shareholder, is thought to have scooped £240m from the deal with his 45 per cent stake.

He clashed with his uncle Toby who pushed for sale in 2002 to rival publisher Taylor & Francis, based at Milton Park, near Abingdon, which had approached the group with an informal offer of £300m.