They were joined by The X Factor judge and Simon's friend, Louis Walsh, who posed with them outside a restaurant in Mayfair, London, last night (28 August).
Lauren - who's believed to be 13 weeks along in her pregnancy - met Simon on the French Rivera last week after finalising her divorce with ex-husband, Andrew.
They've both arrived in London to oversea the launch of The X Factor this weekend.
A friend told the Daily Star, "He is in the UK for a few days – he is going to oversee the launch of The X Factor."
"Simon has also got some other business meeting to attend. But it's entirely plausible that he will want to pop and see his mum and take Lauren along."
These two are certainly looking pretty loved up.
What do you think?
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