Originally Posted by fly-guy

Generally, they should allow for you to carry both the new and expired passports with the visa, but it doesn't hurt to contact the Indian Embassy in the UK and even the airline you are flying to confirm.

Keep in mind, if you do decide to go to India, and leave to visit a nearby nation while you are there, you won't be allowed back into India within 30-days that you left, even if your visa is still valid.