HIV+ and Life Insurance?

My partner has been covered for life insurance by his employer for 15 years. About 5 years ago he contracted HIV and has lived a normal life. 3 years ago he go melanoma cancer and sadly dies 3 weeks ago - the death was not related to HIV. He has a life insurance policy - he died of melanoma, but could the payout be refused as he did not inform the insurance company that he was HIV? He contracted HIV 12 years after he started the policy so I am hoping we will still qualify for the payout.. We are based in the UK.