Near a bike shop in Paris today I saw a motorised tandem!
Fantastic piece of kit with a very large finned aircooled engine at the front driving the rear wheel by means of its own chainset running opposite the pedal chainset and about a 10 litre barrel for fuel hanging off the front handlebars. The rider/driver told me that it was a Derny, French made in 1948. Made a lot of noise - but a nice sounding motor and pulled away from the kerb quite steadily without any pedalling required although the guy was riding solo.
The guy at the bike shop - Bicloune - told me that there were quite alot around Paris and that they were often much older than 1948 and that they had often been used in some famous Paris - Bordeaux race.
A stunning looking old bicycle which I have now added to my wishlist.
And here's a link
http://www.users.globalnet.co.uk/~pattle/nacc/arc0266.htm