Edward Hancock, 45, was accused of spraying weedkiller on Sir Richard Tucker's garden at Stanton, near Broadway, Worcestershire, following a 20-year "clash of egos" with Lady Jacqueline Tucker, a garden designer.

Sir Richard, 77, who presided over high-profile cases such as the Polly Peck fraud trial, and his third wife returned from holiday to find their lawn had turned "orange", magistrates were told.

Mr Hancock, of Northway, Tewkesbury, was employed for 20 years before the relationship between he and Lady Jacqueline boiled over in April after she offered him coffee, which Mr Hancock said gave him a headache. They stopped speaking and after Mr Hancock did not turn up to work, Sir Richard dismissed him by leaving a note on his van, the court heard.

Mr Hancock explained that he only returned to the £1.5 million property after his sacking in a secret attempt to fix the lawn after moss killer he had sprayed earlier – at Sir Richard's request – had begun to turn it "bluey".

He hoped that by putting fertiliser on it, he would repair the lawn in time for a charity open day – there was no malicious intent, he said.

In evidence, Sir Richard said Mr Hancock had been a "good country gardener" around Stanton, in Broadway, for 20 years, but was volatile. He did not disagree with the defence solicitor, Lloyd Jenkins, who claimed that there was a "clash of egos" between Lady Tucker, a highly-skilled gardener, and the tradesman.

He said: "There have been times when my wife had said, 'It's either him or me'." Sir Richard said: "I got on with him perfectly well, but he had to be held with velvet gloves because he was very temperamental and sometimes moody. In the latter years he became very moody and his attitude to my wife became very aggressive.

"They found it difficult to communicate."

The misunderstanding with Lady Tucker on 16 April came after she offered Mr Hancock coffee, and he told her he could not drink it because it gave him a headache. "She determined that as argument," Mr Hancock said.

Mr Hancock said of his attempt to repair the dying grass: "I had a reputation in the village for 25 years. I didn't want my name to be bad because I could see grass was going to die."

He insisted he used phosphogen, not weedkiller. The damage was "too neat and tidy to be vandalism", he insisted.

Carol Francis, the chairman of Gloucester magistrates, said the bench was satisfied that Mr Hancock's spraying had killed exotic plants in the garden borders – but added it was also sure that there was no sinister intent in his actions.

After he was found not guilty of causing £500 of criminal damage to flower borders and a grass verge at Sir Richard's house, Mr Hancock said he was "very pleased" at the outcome.