Geoff Robb tells us that David Cameron promised to call the EU referendum not to deal with splits in the Conservative party, but to prevent losing votes to Ukip (Letters, July 12).

This argument contains a fundamental logical error:

it wasn’t for reason A because it was for reason B. But reasons A and B are not mutually exclusive. It was for both reasons.

Alan Robinson,

Lindley Street,

Holgate, York