Paragraph taken from the Department of Transport website current document titled:
SEARCH AND RESCUE FRAMEWORK FOR THE UNITED KINGDOM OF GREAT BRITAIN AND NORTHERN IRELAND
(My bold)
The MoD has responsibility for providing SAR facilities for military
operations, exercises and training within the UK and, by agreement,
exercises responsibility for the co-ordination of civil aeronautical SAR on
behalf of the DfT. Where the coverage provided by military SAR assets
meets the civil SAR coverage requirements, they will be made available for
civil maritime and land-based SAR operations. The high readiness SAR
assets are SAR helicopters, maritime surveillance fixed wing aircraft and
mountain rescue teams. The MoD also establishes and maintains an
Aeronautical Rescue Co-ordination Centre (ARCC) for the operation and
co-ordination of civil and military aeronautical SAR assets.