No you can leave it on but the lock may weather and corrode over time, also expensive if it gets nicked, save £100 and have a fixed towbar fitted of not already fitted.
Most 13 to 7 adapters are basically the same so try eBay £5-7 then you won’t be too upset when you loose it....looks just like the Volvo one
https://rover.ebay.com/rover/0/0/0?m...2F262979807449
I would give the lock and mechanism a good coat of anti crossing spray before fitting.