RSGB IARU contest group was using call GR2HQ over this weekend. Our UK domestic allocations are GAA-GZZ, MAA-MZZ, 2AA-2ZZ. Re the G series, I’m obviously familiar with GB, GI, GD, GM, GJ, GU, GU, GX prefixes but not GR as used by RSGB. So why, 1) are not all the letters in the G range used and, 2) what was the rationale for suddenly moving to the M series? Any ideas?