Sorry for any confusion I have caused, my book mortars and rockets Chamberlain and gander says there is a mark vii and a mark vii* the first is for the universal carrier, the second * version is for paras, is lighter shorter etc. Wikipedia agrees
I remember seeing a 2 inch mortar in the British Army c. 1980, as I recall (never did use one, I think it was an Armoury NCO showing it to me) it was pretty much just a tube and did indeed have a white line painted on it.
As an aside I seem to remember seeing a documentary film saying that a British Para officer won a Victoria Cross at Arnhem partly for knocking out a German tank while firing a 2 inch mortar from the hip at it. Think he may have disabled the tanks running gear?