Its the annual flag waving - with link up to 'Proms in the Park' around the UK and with the tradional songs (and fun). The 'Fantasia on British Sea Songs' is always great to listen to and the 'race' (see if the audience can keep up with the orchestra).
Available via the internet to the world and broadcast to quite a few countries its a great concert to watch - traditional songs and the tradional audience participation is all part of it.
The 'Sea Songs' start with the bugle calls that were used were 'replied' to by each of 'proms in the park' orchestras. To quote the conductor 'the fifth one is the order prepare to ram, I suspose its played by the horns'.
I do wish that they wouldn't mess around showing clips of things related to the piece at the time - at least its on the BBC and therefore NO COMMERICAL BREAKS.
BBC Proms Webpages