This pen looks like it could be an attempt to copy the design of the 1928 Parker Duofold, right down to the dual bands on the cap. It was made sometime between 1946 and 1955, since this is the time frame for Cursor’s Ltd according to the timeline on this page.
The barrel is labeled “Summit Curzons Ltd. London Liverpool”
The nib on this pen is medium, and very flexible. The sac nipple is cracked, but the damage is inside the sac, so the pen does not leak as a result.