There was always a suspicion that Calf Top in the Yorkshire Dales (Note not "The Calf", which is in the Howgills) might really be a two thousander, but very careful measurement ten years ago by John Barnard, Graham Jackson and Myrddyn Phillips found it just missed mountain status.

The Ordnance Survey measure heights these days using a fantastically accurate GPS system.  They then have to convert their measurements into heights relative to Sea Level (known as the Newlyn Datum).  The mathematical process is called OSGM36(02). 

Now however the OS have introduced OSGM36(15) and this makes the difference - all two centimetres of it!