ocr: HL HM HN HO HP HQ HR HS HT HU HV HW HX HYHZ NA NBNCND NE NGNA NJ NK This series of 100-Kilometre grid squares forms the basis of NF NL NINN NO NP the National Grid, which covers the whole of Great Britain. NQ NR NS NT NU Each square is identified by two letters (as shown opposite). NW NXNY NZ This provides the first two letters of a grid reference. SCSD SE TA SHI SJ SK TETG SMISN so SP TL TM SR SSIST SU TQTR SV swex SYSZ TV