Over on the RC website, Frank has this to say, unhappy days –
“About a month later my pal asked me to ride his shiny yellow Norton. ‘It has,’ he suggested, ‘a bit of a knock.’ Did I have any ideas? I rode it around the ring road as rapidly as I dared. The knock was a big knock; I habitually wear open-face lids and they muffleth not the knockings. The knock was the primary chaincase banging about on the crankcase. Plainly it had come loose. Out with the spanners.
“The reason the chaincase was loose was because it was not bolted to the crankcase. The reason it wasn’t bolted to the crankcase was because the driveside half was from a Norton Atlas. The Atlas crankcase does not fit the Commando primary chaincase. A horrible bodge. He called the shop. It was fine when it left, they told him; he must have messed around with it and broken it. And that, gentle reader, was that.”