Irrespective of their vaccination status, those arriving from UK will have to be in mandatory quarantine at home or in the destination address for 10 days after arrival in India. They will also have to undertake a pre-departure Covid-19 RT-PCR test within 72 hours before travel, another on arrival at airport, and a third on the 8th day after arrival. The new rules come into effect from Oct 4.

from Times of India https://timesofindia.indiatimes.com/india/india-hits-back-10-day-quarantine-mandatory-for-uk-nationals/articleshow/86680946.cms