Nicholas van Hoogstraten went "ballistic" when the building work for a luxurious home on his estate went wrong.
The mistake precipitated his split with architect Anthony Browne, who designed his unfinished £28 million palace near Uckfield.
Hoogstraten's current architect, Mark Hylton, was giving evidence at the Old Bailey, where the millionaire tycoon is accused of murdering businessman Mohammed Raja.
Mr Hylton said there were major problems with pillars and floors within the grand Boat House.
Asked by Richard Ferguson QC about Hoogstraten's reaction to this, Mr Hylton replied: "His response was quite unforgettable really.
"He went ballistic - very angry, and with very good reason.
"He said 'Who's fault is this? Why has this happened?'."
Mr Hylton said Mr Browne did not "acquit himself as well as he should" to the project.
The jury earlier heard alleged hitman Robert Knapp believed he was going to move into the Boat House, although Hoogstraten denied this.
Mr Hylton confirmed he had seen Knapp on Hoogstraten's estate, where his mother has a cottage.
Mr Hylton, who is appearing before the jury for a second time, said he was told he would be giving evidence at the end of last year. In cross examination, the court heard that after agreeing to testify, Mr Hylton received a £5,000 loan from Hoogstraten to buy a car.
Mr Hylton insisted the loan was "not consequential" to him taking the stand.
The jury also heard from Hoogstraten's Hove-based solicitor, David Englehart.
He told the court the tycoon's illegal disputes with Mohammed Raja were a small proportion of his total litigations.
Hoogstraten is accused of hiring two hitmen to kill Mr Raja in 1999 after he accused the millionaire of fraud.
Mr Englehart said he represented Hoogstraten in litigations with Mr Raja over at least four properties including one in Roundhill Crescent, Brighton.
However, he added the court time with Mr Raja amounted to just five per cent of his firm's actions for Hoogstraten. And he said Hoogstraten also employed a number of other solicitors in Brighton and London.
Hoogstraten, of High Cross Estate, Framfield denies murder and conspiracy to murder. David Croke, 59, of Bolney Road, Moulsecoomb, and Robert Knapp, 53, County Limerick, deny murder.
The trial continues.
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