Parliamentary Voting System and Constituencies Bill

I am quite happy to recast my argument not in terms of prime numbers and numbers of seats, but to come back to the question of why that number of electors should be chosen. What is the rationale? Why that figure, as opposed to 75,000, 72,000, 80,000, 85,000 or 90,000? That leads to a subject which I am sure we will come on to: the degree of tolerance around that figure.