Mr Rowland, long one of Britain's most controversial, charismatic and colourful tycoons, was sacked by the group at a 10am board meeting for "continuing public and irreconcilable differences with the company".
He left Lonrho's Cheapside offices in the heart of the City for immediate talks with his lawyers and supporters, severing his 34-year link with the company. He later said he would pursue Dieter Bock, Lonrho's chief executive, "to the end of his days", adding: "It's the act of a desperate man. I'm going to get the best QCs and my lawyers to sue Lonrho - and Bock in particular."
The board's decision appears to have been prompted by an article in Focus, a German magazine, at the weekend, which was followed up by the Mail on Sunday.
The company said that Lonrho and Mr Bock would sue the magazine and the Mail over the articles, which made a series of allegations about Mr Bock's complex web of property companies on the Continent.
Mr Rowland, famed for his colossal feuds with other businessmen such as Mohamed Fayed, owner of Harrods, has been involved in a sporadic and increasingly bitter war with Mr Bock, the German businessman he brought into the company in 1993.
Peace appeared to break out last autumn, when Mr Rowland agreed to give up his position as joint chief executive and retire at the annual meeting later this month. In return he was to be appointed president and would keep his £1.5m salary and benefits package until the end of this year. Sources close to the company said he would now receive no compensation.
Mr Rowland denied having anything to do with the articles. They concentrated on the sale by Lonrho of 4,300 flats in southern Germany in 1993, alleging that Mr Bock had benefited personally.
Lonrho said yesterday: "It is wholly untrue to say that Mr Bock or any company or entity associated with him was a beneficial purchaser or benefited in any other way [from the sale]."
It added that Mr Bock had commissioned a report for the board from the company's auditors, KPMG, on the deal.
"They have confirmed that the accounting treatment and disclosure of the transactions in the 1993 accounts of Lonrho is fully appropriate and consistent with the facts," the Lonrho statement said. "The sale produced a profit of £8m, which Lonrho believes reflects a good price, particularly against the background of previous unsuccessful efforts over a long period to achieve such a sale."
The flats were sold to Klaus Hahn, a German property developer. It is understood that negotiations on the sale began before Mr Bock's arrival at Lonrho, but he helped to conclude them and provided a nominee company for Mr Hahn to acquire the assets.
Sources close to Mr Rowland said he had been utterly unprepared for yesterday's showdown, which came after a meeting of board members at 7.30am. It is understood that lawyers and advisers, including KPMG, bankers Morgan Grenfell and brokers James Capel, worked through the night on the day's statements from the company.
One director, John Hewlett, one of the few Rowland loyalists left at Lonrho, refused to back the resolution removing Mr Rowland, who still owns a 6 per cent stake in the company.
Mr Rowland has long maintained that borrowings made by Mr Bock to buy his near-19 per cent stake mean the German businessman aims to break up Lonrho, a strategy Mr Rowland opposes. "Bock needs to get rid of me because I was the only one who stood between him and Lonrho's assets," he said.
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