Trevor's comment above, in the 1916 Primus No.2 thread, got me thinking. My oft used but very basic oven (above & below) is only ever set up on an auto-start Patent Pyro, which only has a '00' size burner. Not only that but it never even gets pumped, I find the level of the self-pressurised flame more than adequate to heat and maintain the oven at a perfectly adequate c.200°C. Nothing Gordon Ramsey but absolutely fine to heat a pie or pastie, so why the need for even a No.1 burner never-mind a No.2! ?