This is from the site Bring a Trailer (https://bringatrailer.com/) ...
This 1954 Ariel Square Four comes attached to an ultra-cool Canterbury tandem seat sidecar and what looks like most of its original furnishings. Powered by one of the most unusual engines ever dropped between two wheels, the “Squariel” features what’s in essence two OHC parallel twins occupying the same crankcase. These MkIIs (introduced the previous year) had separate cylinder barrels and four exhaust pipes as opposed to the monobloc and twin pipe setup of the MkI, but both designs utilized dual, geared crankshafts and a single cylinder head, and Squariels were some of the fastest bikes in Europe during the era. This one looks like it could be a survivor or an older restoration–either way it’s super cool, super unusual and would likely be a great way to strike up conversations at your next local cruise-in. Find it here at Yesterdays in Nederweert, Netherlands for 14,950 euros (~$16,500 USD today). Special thanks to BaT reader Kyle K. for this submission.
The pair exhibit the sort of warm, gentle patina typical of machinery left unattended in a clean, quiet corner of a garage or workshop for a long time–virtually all of brightwork is dulled and paint could use a good compounding, but there’s nothing which suggests that the duo have been neglected or abused. No word is given on when the bike was last started or taken out on the road.
There were a large number of sidecar manufacturers in Postwar Britain, and Canterbury and Watsonian were two of the more prominent. These rather awkwardly named “Double Adult” models were constructed over a steel tube frame and featured tandem bench seating for two, a single entry door, a small trunk, no less than seven windows, and a removable canvas roof for the occasional sunny day. An outboard wheel brake was an available option, but it’s not clear whether this one is so equipped.
The door looks big enough for easy entry, and we’re guessing the front seat back folds down for access to the rear bench. Legroom for both occupants looks generous, with a bit of extra room for a couple of small bags.
The engine is essentially two parallel twins sharing a crankcase. It displaces 1000cc and powers the Ariel with roughly 40 horsepower and a good deal of torque–these machines were known to be capable of getting underway from a standstill in top (4th) gear. They could also easily surpass the 100 mph mark, though we’d imagine even going half that speed in a flimsy old sidecar would be equal parts fun and terrifying.