A street was cordoned off and the bomb squad called after a businessman found a flashing device under his car - which turned out to be a tracking bug fitted by his suspicious wife.
William Sachiti spotted the cigarette packet-sized GPS tracker and feared the worst after previously providing security and anti-fraud devices for banks.
The entrepreneur, who once appeared on TV's Dragons' Den, had recently begun working late and his wife, Dr Diletta Bianchini, thought he was having an affair.
So she hired a private investigator, who then bugged his silver Lexus SC430.
When Mr Sachiti spotted the tracker he went to the nearest police station and the High Street in Sutton, Surrey, had to be shut down.
He told the Daily Telegraph: "(It) was the wife who hired someone to follow me as she was concerned about my new ambiguous work hours.
"She may well have thought I'm having an affair but I'm not.
"My wife has always been that sort of person who has wanted to know where I am."
As police began to cordon off the area, Mr Sachiti telephoned his wife and she confessed.
"I'm just so sorry it happened.
"It was a huge mistake and I was out of my mind," she told the paper.
A spokesman for Scotland Yard said: "Police cordoned off the immediate area to traffic and pedestrians.
"A cordon was put in place at the traffic lights in Cheam Road at the junction with St Nicholas Way to prevent traffic from going along Carshalton Road.
"Officers were also positioned near the junction of Throwley Way and Carshalton Road to restrict the movements of pedestrians.
"The bomb disposal squad, London Fire Brigade and London Ambulance Service were called but cancelled shortly after when police officers were informed by the driver's wife that she had arranged to have a tracking device fitted underneath the rear of her husband's car.
"The security company who had fitted the device was contacted and described exactly what the device looked like - a cigarette packet-sized box with two magnets attached - and exactly where the device had been installed."