Frank: that "fat Lancaster" was the CL-33 of 1953 for the RCAF's Lancaster 10MP replacement contest.
Canadair first submitted the CL-29, a stretched and re-engined North Star (with R-3350-85s, Hercules 763s, or Centaurus 661s). Both that CL-29 proposal and a Super Constellation derivative submitted by Lockheed were rejected.
The RCAF's favoured concept was a Bristol proposal to adapt the Type 175 Britannia. Other than minor concerns (like sufficient aileron control for low flying), the RCAF's major concern was the relatively-high operating costs of any Britannia derivative.
In 1953, Canadair produced the CL-33 as "a minimum cost alternative" to the Britannia-based maritime patrol aircraft. To be powered by 3,500 hp R-3350-32W (34FS) turbo-compounds, the CL-33 was to have weighed about 9,000 lbs less than the Britannia derivative.
'Canadair: the first 50 years' (Pickler/Milberry, CANAV).