This is an exaggeration of the slowness of stage coaches and the speed of railway trains. London to Edinburgh took 3 or 4 days by coach c1850 [i]. In 1845 (just before this song was written) it took 10 hours to get from London to Newcastle, some considerable distance short of Edinburgh [ii] [i] https://reginajeffers.blog/2017/04/25/stagecoach-travel-during-the-regency/ [ii] Freeman, Michael and Aldercroft, Derek The Atlas of British Railway History (London, Guild Publishing, 1985) p27