Stephen Young, a father of two, shook his head as the jury returned guilty verdicts at the end of a three-and-a-half week trial at Hove Crown Court, East Sussex. The decision was greeted with cheers from the public gallery, where Mr Fuller's family had sat throughout the trial.
The court had been told how Young, 35, a gun enthusiast, shot the couple at their home in Wadhurst, East Sussex, in February last year as part of a plan to rob Mr Fuller to get cash to offset huge businesss and personal debts.
Mr Fuller, 45, who was known to boast about and exaggerate his wealth, was shot through the back and died immediately as the bullet pierced his heart. His wife of six months died after being shot four times as she tried to flee her killer. Young fired the last bullet through the back of her head after she had crawled to her bedroom and dialled 999 in a futile attempt to call help.
A tape of the call, which was recorded by British Telecom, was played during the trial. Jurors heard Mrs Fuller's last 'squeals' for help before the final shot was fired. Young, of Heskett Park, Pembury, Kent, then tried to make the killings look like a drug-related crime by scattering fine powdered sugar over Mr Fuller's body.
He would probably have escaped detection but for two details he was unable to foresee. One was a tape-recording of a conversation he had with Mr Fuller on the night before the killings in which they had agreed to meet at the cottage the next morning. The tape was played on the Crimewatch television programme, and Young's voice was recognised.
He was also unaware that a bank's security system had filmed his car entering and leaving Wadhurst, with an hour's interval in between.
Young, who denied both murders, claimed in court that he found Mr Fuller dead when he called at the cottage. As he left the house he saw a mystery face at an upstairs window, he said. Later, he claimed, he had received threatening phone calls, which persuaded him not to tell police what he saw.
After the verdict Tom Fuller, 40, one of Harry Fuller's brothers, said of Young thought his brother 'was easy prey for a lot of money. This verdict is a great weight off our shoulders'.
Nicola Fuller's father, Michael Johnson, said: 'The verdict doesn't change things for us at all. We can't bring Nicky back but it does take one evil person off the streets.'
Detective Chief Superintendent Graham Hill, who led the inquiry, said: 'Outwardly Stephen Young was a very responsible family man who was well- liked by his clients and people in Pembury. There was a totally different side to him and it is that other side that very few people knew about.
'These were cold, callous and calculated murders and all the evidence is that they were pre-planned.'