World’s Longest Bus Route was from London to Kolkata and back to London. The Bus Service Provider named Albert Travel facilitated the bus service in 1957 from London, England up to Calcutta (Kolkata), India.
The Journey was about 50 days. The Bus crossed around 10 countries before reaching India.
The Bus even had facilities like Bunk beds, Fan, Kitchen etc.
Extra’s: Some might say London is an Island, and there was no Road to travel between London and other Countries, but the bus would have been boarded in a ship to Belgium and from there the real road trip would have started which would finally end in Calcutta, India.