Thanks for the reply Baracuda. In a way it makes a bit of a mockery of the whole idea of a DB scheme. The example I'm thinking about is a situation where the scheme is not allowing early retirements even though the company is posting big profits.
If there's no obligation on the employer to fund the scheme to the level required, then the so-called "guarantees" of a DB scheme are worthless. Member has annual statements which used to include a paragraph about possibility of early retirement with Trustees' consent.
So it would seem that DB scheme booklets should contain a line that says "At retirement you will receive a pension of 1/80 of your scheme salary for each year of service...provided that the employer can be bothered to fund the scheme to do so."
Thanks again for the information, even if it wasn't what I wanted to hear.