Property developers Paddy McKillen and the billionarie Barclay brothers are at loggerheads this weekend over the control of three London hotels - Claridge's, Connaught and Berkeley.
The Belfast-born bussinessman is testifying against a verbal attack from financier Dereck Quinlan, a key ally of the Barclay's brothers.
Mr Quinlan spoke up after the London Supreme Court into refused Mr McKillen leave to appeal a decision by another court over the future of the €1.2bn company, accusing him of being engaged in an "ongoing campaign" against him which he described as "absolutely hopeless and doomed to failure".
"It is unfortunate that Mr McKillen's behaviour against me has become somewhat obsessive. Surely he has more pressing concerns, such as finding a way to repay his huge debts to the Irish State?" Mr Quinlan said to the Irish Independent.
Mr McKillen retorted by saying "Derek Quinlan is complaining about a situation that he created and I have been forced to defend against. He joined with the Barclays who planned to make a profit of hundreds of millions from the deal," said Mr McKillen. "Their hostile takeover was launched almost three years ago and I have been forced to defend against their actions since then through the courts. I have no intention of giving up and will continue to take whatever legal action is needed to protect my business."