I have a very similar pen - slightly different button, cap end and clip, but the same overall appearance, including the section shape. Mine is marked 'The Durable Pen' and 'Made in England' but I wasn't able to ascribe it to a particular company. Closest possibility was the Desmond Precision Co Ltd, who are listed in TEFPI as producing a 'Durable' ballpoint pen in 1947.
Other aluminium pens of the same era (late 1940s) were the Homelink pens made by Kagan & Co. These were available in aluminium, polished silvery colour or anodised in various colours, which would have been quite pretty I think. All the Homelink pens appear to have been lever fillers, so I doubt this is one of theirs.
That’s really helpful, thanks!
I’m having an absolute bugger of a time getting the section out - do you think there are any particular risks of carrying on with dry heat and trying to unscrew it?