For many years the pend was the only way to get from High Bonnybridge to "Low" Bonnybridge, until the bridge was built over the canal.
Nowadays you can still walk through the pend and, if you're brave and the water is low, you can drive a car through, trust me 
The pend was named The Radical Pend to commemorate the Battle of Bonnymuir in 1820. On 5 April 1820 a group of striking weavers (The Radicals) were intercepted on the way to the Carron Ironworks. The group had been infiltrated by government agents. The men, who were protesting about the right to vote, were ambushed by an armed force outside the village of Bonnybridge. In the ensuing struggle, at least four of the weavers, a police lieutenant and sergeant were badly wounded. Three of the rebel leaders - Andrew Hardie, James Wilson and John Baird were arrested and later executed.
The water that flows through the pend originates from St Helen's Loch and flows both under and over ground from the loch to the pend in man made channels.
The cache is a small magnetic micro.
Congrats to Scotbrain for FTF!