Possible Clues:

• Maker of Rolls, say, with large wheels and brown line in London
• London Underground line that runs between Harrow & Wealdstone and Elephant & Castle
• Underground line from Harrow & Wealdstone to Elephant & Castle
• London Underground line with terminus at Elephant and Castle
• Producer of bloomers - ladies' line
• Line used by one who needs, say, to reach toilet!
• Line to bear king and queen within
• John following tradesman's line
• Underground line
• London Underground line represented in brown