Mrs. Percival is raising money for a new sports pavilion but, despite Bob going on a sponsored run, she is still far from reaching her target. The Machines volunteer to undertake a 'sponsored demolition' of the old pavilion. During a practice session, Lofty loses control of his demolition ball so Bob fastens it tightly to avoid further accidents. He absent-mindedly slips the spanner into his tracksuit pocket and takes it with him on his sponsored run.  At the pavilion, Lofty gets his cable tangled in some rugby posts. The spanner is missing from the toolbox, and Wendy realises where it must be. She sends Bird to find Bob, who jogs over to the pavilion and helps untangle Lofty, then goes back to complete his run. Mrs. Percival is delighted to announce that since Bob has run twice as far as originally planned, enough money has been raised to build the new pavilion.