I also ran the Downham 5.5 mile race from 1984 through to 1991 and was latterly organised by Colin Taylor of Clayton Harriers.
There was poor visibility in 1991 and some runners ended up in Barley. Colin got a lot of stick that year from runners for not 'flagging the route' so he threw in the towel and there was no race in 1992.
In 1993 he resurrected the race, but the route was extended to 6.5 miles with an extra climb in the middle. It was last run in 1997.
I too can recall running the plank, over the wall / barbed wire, and the nettles too! Great times were had before Mr Health & Safety got involved
The only race that starts from Downham now is the Pendle Cloughs race ~ this year it's on Sunday 4th June at 11.00am. It will be good to see some old and new faces there.
http://www.fellrunner.org.uk/races.php?id=5306