It's called
Sailing By methinks. It is the music played as the intro to the nightly shipping forecast on BBC radio. (Just think what foreigners miss

)Foreigners should be aware of this nightly ritual.It is part of British life. The shipping forecast is for, well, shipping. It's to tell mariners the weather which is present and forecast for the shipping areas around our coast and in the immediate areas beyond.The sea areas have names mostly referring to landmarks or coastal features such as river mouths. Tyne (river),Tees (river),Cromarty (part of Scotland), Forth ( estuary), North Uitsere, South Uitsere ( areas of sea off southern Norway), Dogger (a sandbank), German Bight (an indentation on that coast) and so on. (Many of us poor Britons can recite the list in sequence, which never varies and runs clockwise from the North East

)It's full of nautical language like 'North-easterly veering easterly'. This is followed by the inshore report, which is even more cryptic to landlubbers and is all about visibility, and the like, at coastal weather stations.
The forecast is still given, though it must be less relevant to seafarers than it was now that ships have onboard computers and access to constant weather information from satellite services etc
Secondary purpose? Probably the shipping forecast marks the end of daytime broadcasting on Radio Four, when the World Service takes over on that channel.