Immigration

 He calls me a "self-appointed immigration tsar". I have appointed myself to no such position; I merely express an opinion, which carries no more weight than anyone else's.

He says that I always try to "obfuscate the debate into racism or benefit scrounging". I have done nothing of the sort. I merely pointed out that, contrary to the opinions expressed by many Ukip supporters, immigrants are not a burden on the taxpayer, but contribute far more in taxes than they take in benefits.

This is a fact that even Nigel Farage has acknowledged, though he added that "some things are more important than money".

As for racism, I made no mention of it; but I have frequently acknowledged that it is not necessarily racist to be concerned about current levels of immigration.

Dr Sparks goes on to expound a bizarre theory that people have evolved "to suit local climates" and should therefore stay where they are.

Humans have migrated across the globe for thousands of years. Fair-skinned people have long lived in "hot, sunny countries". Black and brown-skinned people have lived in Britain for centuries.

Some are the descendants of African slaves, traded and exploited by the British, who gained vast wealth at their expense. Others are descended from the five million volunteers from the British Commonwealth who fought for Britain in two world wars, the Lascar seamen who were the mainstay of the Merchant Navy during the Second World War and the thousands of Bengalis recruited to work in England's cotton mills.

No wonder the fastest-growing ethnic minority in Britain is mixed-race.

Still, it was kind of Dr Sparks to describe my letter as "didactic", which means "instructive" or "enlightening". It comes from the Greek didaktikos, which means "skilled in teaching".

I wonder what sort of doctor Dr Sparks is. Perhaps he will enlighten us?

Pete Winstanley, Durham.