American socialite Silverman, 44, and Cowell confirmed their romance in 2013 and became parents to a son, Eric, on Valentine’s Day in 2014.
Eric is named after Simon’s late father and Silverman has a child, Adam, from her previous marriage.
The happy couple, aged 62 and 44 respectively, zipped along the street in the wake of the happy news, on which, Simon broke his silence earlier that day when he was asked if the reports were true, after which he said: ‘What do you think?’, before replying to congratulations by saying: ‘I really appreciate that’.
The latest sighting, during which neither party used a helmet for the ride despite Simon toting the protective headwear on his bike handle, comes after insiders stated that the past two years have helped Simon ‘learn what’s precious’, while their friends state that they are ‘soulmates’ and each other’s rocks.
On Tuesday, it was revealed that Simon had popped the question to his girlfriend during a trip to Barbados, before Lauren was spotted out in Malibu the following day flashing her $3.4million (£2.5m) engagement ring, although she went without the ring during her earlier bike ride with Simon.