Worn by: Colin Firth as Ben
Reference: Omega Speedmaster
Brand: Omega
Around the 25-minute marker, there's an emotional scene where Colin Firth (playing Ben) hugs Nicole Kidman (playing Christine) in the pouring rain and for a good few seconds, we have a nice frontal view of his Omega Speedmaster Professional.
Source: https://www.fratellowatches.com/speedmaster-in-movies/