Some Tube stations are so close to each other it's actually quicker to walk between them than change lines. Distances 15 minute walk and under, please. (We should probably leave out NR stations to keep the list manageable.)
- Highbury and Islington and Angel
- Queensway and Bayswater
- Paddington and Lancaster Gate
- Monument and London Bridge
- Leicester Square and Piccadilly Circus
- Leicester Square and Covent Garden (just 250m).
- Covent Garden and Piccadilly Circus
- Covent Garden and Charing Cross
- St Paul's and Mansion House
- Cannon Street and any of Bank, Monument or Mansion House.
- Warren Street, Great Portland Street and Regent's Park.
- Aldgate, Aldgate East and Liverpool Street
- Liverpool Street, Moorgate and Old Street
- Euston and Euston Square
- Hanger Lane and Park Royal
- West Acton and North Ealing
- Charing Cross and Embankment
- [New Cross]? and [Deptford Bridge DLR]?
Please add any more that you know of.
See also this London Tube Map with Walklines.