The Race Relations Act 1976
Crime and Disorder Act 1998
It is illegal to discriminate against a person because of their race (and other factors); it is illegal to incite racial hatred; it is illegal to racially harass a person (you can call him a b***ard but you can't call him an Irish b***stard) but it is not illegal to make racist comments in a private setting - that is exercising your right to free speech.
I assume you were aware of the recording and consented to it. The recording is the property of the person who made the recording in much the same was as a photogragh is and you can't demand it be destroyed.