The trouble with the Roman numerals is that they can be misread, particularly in the case of II Squadron.
There was a thread here some years ago bemoaning the inadequacies of the MoD's directory enquiries type service. Someone had asked to be given the number for 5 Squadron.
The operator denied that such a squadron existed (it was still flying the F3 at the time). To cut a long story short, caller ended up asking if the directory happened to have a 'V[ee] Squadron' (which, funny old thing, it did)...