Some 200 people from another train a short distance behind (Connex South Central service from London Bridge to Guildford train) were initially left unsupervised, and had to find their own way to evacuate themselves in the inclement weather.
The passage describes a situation where 200 passengers on a separate train, travelling on the Connex South Central route from London Bridge to Guildford, were left without assistance during inclement weather and needed to evacuate independently.