Are any London boroughs outside the M25?
Are any London boroughs outside the M25? North Ockendon is the only inhabited area in Greater London outside the M25 London Orbital Motorway.
Is Windsor inside the M25?
Windsor is in Berkshire, well outside of the M25, and not really close at all to London. It does not even have a London postcode. It is west of Heathrow Airport, and the London Underground only stretches as far as Heathrow as well, so is not on the London Underground network.
Why is M25 called M25?
How the M25 got its name. The same principle explains the M25, which at its oldest point (the section crossing Surrey) follows the path of the older A25. These roads are all in the South East, which forms Zone 2 of the country's motorway system. This explains why they all contain 2 somewhere in their name.