There is an area in mainland GB (of the 1km square gridded .shp file) which is with missing polygons, so it seems like there is a "hole" in minland GB. For comparison, such area does not exist in the 5km square gridded.shp file

Hello, practically 2/3 of the 25km tiles have the two letters at the beginning of the tile ref missing. Only 4 numbers available.

Each tile in the 5km grid is also divided in four 2.5km x 2.5km quadrants with the same name + "ne" for North East, "se" for South East etc. If you still have the code for generating the other grids, it would be great to add this to the collection. Thanks!

Hi @charlesroper, what you've published is very useful, I've found this by reading the StackExchange thread at http://gis.stackexchange.com/questions/21/ordnance-survey-grids-download-or-generate . The question you put 5 yrs ago was likely the original problem you had that brought to the creation of the files. Oddly enough, the answer someone got back to you is your own solution :-)

... but where does the data come from? You must have calculated it from Ordnance Survey's own definition of the grid, or perhaps you found some intermediate work. If you shared a little more it would be easier to trust the robustness of your work, particularly to build on top of it, as I would like to do.

Please tell us more!