Cover letter for short story submission.

Hi! Does anyone know whether it's customary in the UK to include a cover letter when submitting a short story to a magazine that publishes fiction? I've read the submission guidelines for several magazines, but none of them mention this. I'm assuming it's best to include a brief cover letter, but am still unsure of what to write - should I summarize my story, give an account of who I am/ what I do, or just keep it really simple? Any help would be much appreciated, thanks.