I stumbled across this today looking for something else -
http://lanternimages.lancashire.gov.uk/image.php?i=20686&r=2&t=4&x=1
great shot of Nelson in its heyday. EDIT ...Glen tells me this was taken at the first ever Nelson meeting in 1967

The website itself is a treasure trove of Lancashire images, see -
http://lanternimages.lancashire.gov.uk/
If you search for "Nelson", it shows lots of old pictures of the annual fair, which was on the old track Car Park over the road in the "pits"

cheers,
Les