Northern Ireland has a strange approach. Generally they follow a pre-1963 county-based system in monotonic sequential order but occasionally a profitable prefi

Northern Ireland has a strange approach. Generally they follow a pre-1963 county-based system in monotonic sequential order but occasionally a profitable prefix arises; recently BIG nnnn where nnnn is integer. So they can reserve the 'nice' ones in the sequence e.g. BIG 1 and sell those on the market. But they don't sell them in advance of sequence.