Pindar is located approximately 200 feet beneath the Ministry of Defence's Headquarters in Whitehall and has been operational since December 7, 1992. The bunker accommodates roughly 400 bunks, though the specific contingency plans for its use remain undisclosed. Access to Pindar is restricted to ministers, senior military and civilian personnel, plus service and civilian operational and support staff.
The UK Prime Minister is the only person granted a bunker for their family within the facility. According to Daily Express - UK News, Colonel Philip Ingram described that there will be an access list and a standby list for Pindar, and if the Principle is killed, the Deputy has to come in. He also noted that the standby list might not reflect those currently in government and could include someone from the Opposition, based on who is the best person for the job, but the exact criteria for this list are unclear.
This is Britain's worst-case scenario bunker. It's there to deal with a full-scale nuclear strike. It's a last throw of the dice situation to try and keep things moving and the country running.
Pindar features a broadcast studio, but details on other facilities, such as how the bunker is supplied and maintained for long-term survival, are not publicly known.
There will be an access list and also a standby list for someone who can't make it. If the Principle is killed, then the Deputy has to come in.
It might not reflect those that are currently in government. It could be someone on the Opposition. It will be the best person to do the job.