The posts revealed the discovery was made after an unmarked unit had clocked a Mercedes doing 103mph in Eastbourne.
The officer was reported to have drawn level with the vehicle, still at high speed, to find the driver and his lady passenger 'busily engaged'.
"He's been reported for his speed, as well as driving without due care and attention," it added. "Plus it turned out he wasn't insured to drive the car, so we've seized it. He's probably had better nights..."