Claim: The North Magnetic Pole has shifted, and is midway between King's Cross and Euston Underground Stations.

Facts required for proof: The North Magnetic Pole moves about in an elliptical path with a maximum radial distance of about 80km coinciding with movement about the sun (ignoring polar drift for now), and as such the Magnetic North Pole is considered to be on average an area rather than a point. A compass needle points towards magnetic north, and once you are atop the magnetic north pole the only direction it is possible to travel is south (i.e. away from magnetic north).

Evidence for my highly scientific claim: If you are at King's Cross, you board a southbound Victoria Line train, and travel one station to Euston. Change to the southbound platform for the Northern Line, go one stop, and you're at King's Cross. Repeat ad-nauseam until you've spent all day heading south and have gotten nowhere.