A spokesman for Essex Police said:
"Evidence from fire scientists has indicated that the likely cause of the fire was malicious ignition.
"Detectives know that there was a burglary at the house on the same evening/early morning of the fire and are re-appealing for information and witnesses."
More top news
Arsenal managed to beat Everton at the weekend but it wasn't enough to finish in the top for the first time in Wenger's time at the club.
The entertainer was held for the murder of Stuart Lubbock, who was found dead in his swimming pool in 2001, but never charged.
Although the diamond was believed to be cut in the 19th Century, its history and how it arrived at the car boot sale is unknown.