The Capacity Market
The Government introduced the Capacity Market to manage security of supply of electricity and ensure that Britain has enough reliable capacity to meet demand at least cost to consumers. The Capacity Market ensures electricity supply security by providing a payment for reliable sources of capacity.
The Capacity Market is designed to:

make sure there is enough reliable capacity to meet electricity demand.

procure only what is necessary, using competitive auctions held four years before the delivery year (T-4 auction) and a year before (T-1 auction)

accept various technologies from power generators who can commit to being available