Well not Ultima! Close, but no bananas. (There's a phrase that Google translate will have problems with.)
Not, it's not British, although it could be. Stick with me.
Zundapp in Germany patented a forged frame in 1929. The frame described in the patent used steel forgings for all parts of the frame, which was bolted together from a number of smaller parts. Even the fork blades were steel forgings: one for each side. The main spine of the frame is the parts which encompasses the steering head, the tank rail, and the short part of the down tube. These are labelled 1, 2 and 5 in the patent drawing. Everything else bolts on to this.
In real life Zundapp built a range of models using frames like this before they went to pressed steel frames. The photo of the 1929 Z200 should look pretty familiar?
And the British connection? At the 1930 Show the Newmount motorcycle was announced: basically a British-badged version of the Zundapp. One of its features was that the fork blades were identical left to right. Very useful.
So there you have it: Zundapp or Newmount.
Mystery solved?
Leon