Father Passed Away In India. No Cause Of Death On Death Certificate. Insurance Requesting

Hi, I'm hoping someone who has experienced a similar situation, or a professional, can help me.

My father lived with me in England, and went on holiday to India in December. He sadly passed away and was cremated abroad. I have the death certificate from India, however it does not state the cause of death on it.

My father has life insurance in England, however they're asking for confirmation of the cause of death before they can proceed any further. I've spoken with the doctor who performed CPR on my father (in India) and he said he can write me a certificate but as he was not his patient he can't confirm cause of death was heart attack, only expected heart attack. He did not do an ECG as he wanted to perform CPR straight away.

He's asked me what I would need the certificate to say and what the insurance company need exactly. Would anyone have some advice on what I can request, so that the insurance companies criteria for "confirmation of cause of death" is met? Do I need to get something written from India and take it to my dad's GP in UK to then confirm the reason? Or do I ask the doctor in India to write that the cause of death was a heart attack due to all the symptoms shown?

There is no body any more so no post mortem was done, and one can no longer be done, sadly.

Thank you in advance