The only possible explanations are: 1. One of the two is travelling faster than Usain Bolt can sprint. 2. Scotland Yard has issued doctored CCTV images/timeline. I am going with the Met issuing doctored images.

The Metropolitan Police had issued two airport CCTV images of the suspects in the Salisbury Skripal poisonings with the date/time indicated in the images. A representation of the Met was quoted in the cited article: "The images of the two suspects at Gatwick are taken from two different cameras covering separate lanes at the point passengers exit from international arrivals."