British citizenship and India travel

[NCL123]

Hi,

My son has traveled to India in August on Indian passport and we have received his naturalisation certificate and British passport today (October) at UK home address. I have few queries regarding traveling on Indian and/or British Passport.

1) At present my son is in India so can he travel back to UK on Indian passport which he has used earlier to travel to India? His British passport is arrived in UK home address and he do not posses it physically as he is in India so in this scenario I guess he can use his Indian passport to travel back to UK. Please advice me further on this matter.

2) In case If it is mandatory to use British passport to travel back to UK then Immigration officer may not allow him to travel on British passport as he do not have India visa stamped on his British passport. I guess it will be a big problem for him at the airport.

So what is the best way forward for him to travel back to UK from India. Can anyone guide on this matter.