Hooked teeth

The cognoscenti will recognise this as a left hand chain ring - only found on tandems....
We went out on the tandem today and took a different route to Thaxted which involved a short but unreasonably steep rise, went for the middle ring and zilch, cable went slack but the front derailleur stayed put. Much honking and we cleared the crest but I realised the tandem's in need of some TLC.
Gave it the once over when we got back and cleaned, oiled and greased the parts that ought to move. A clean of the two chains revealed that the front chain is shot and so are the two sprockets, the front one (mine) has hooks on the back of the teeth, the rear one (the governor's) has hooks on the front......seems there may have been a bit of slacking going on back there!
This is a nice excuse to go surfing the bike websites in search of new rings and about forty foot of new chain!!!!!