The railroad companies needed to keep precise track of London time, so they would send out people from London on trains with precisely tuned watches so that regional clocks like this one could be kept up to date. These timekeepers would arrive in a given town, hop off the train, and go show their watch to the station masters. Then, those same watch-bearing travelers would hop onto another train to a different city, updating clocks across the country, one station at a time.
I would have never thought this is how time was determined but there are different ti e zones and they have to b determined some how.