Thanks for all your replies.

Another question if I may, my flight from LHR is arriving at 0330 in Terminal I. I was looking at the 0640 AI flight from Terminal D.

Will that be enough time to go through immigration, collect my baggage and check into the domestic flight? Are the terminals close by or is it like heathrow I will be flying business class internationally if that makes a difference.

Also, is there a time you need to check in by on Indian domestic flights?

Thanks
Kevin