Longest Line

The Longest tube line in London is the Central line. It goes from West Ruislip to Epping for about 76 kilometres or 46 miles, a distance that is considerably longer than London itself. The reason it is able to cover that distance is because it doesn't go in a straight line but sort of zig zags across it. 

The Longest Journey time wise would be on the district line because it goes to 80 stops and takes about one and a half hours. 

~ image generated by artificial intelligence (chatGPT) 

The Elizabeth line goes from Reading("reding") to Shienfield in Essex, 100 kilometres or 62 miles. (You would need to change trains at one of the tube stations to get to Shienfield.) It acts like a tube line for part of the journey but is more like a commuter train. It covers the whole journey in less than 1 and a half hours