Joe, I'm intrigued by this one.
Following the failed devolution referendum of 1979, we had four successive governments voted in by English electors. Scotland voted Labour four times and got a Conservative government four times. In 1992, after the fourth 'unelected' government, some SNP campaigners set up a caravan to hold a Vigil outside the Royal High School in Edinburgh (proposed site for a Scottish Parliament) to be a campaign headquarters for the Devolution / Independence cause.
The caravan was taken away after the successful Devolution referendum in 1997 and the establishment of a Scottish Parliament in 1999 (at Holyrood, not the Royal High School as previously proposed). I know that the caravan has been preserved somewhere, but I am not at liberty to say where.
But it was an SNP thing, not a Labour Party thing. Dennis Canavan was a vocal exponent of Devolution and a Scottish Assembly / Parliament, but he was nothing to do with the caravan or the Vigil for a Scottish Parliament.
I suspect the cartoonist knows the words 'Canavan' and 'Caravan', but doesn't understand the back story. Dennis Canavan may have supported Devolution, but he was opposed to the guys holding vigil in the caravan, and they were opposed to him.