On attempting to bleed the brakes (with Draper brake bleeding kit with one way valve) starting at the rear right (as per Haynes manual).
All I get is a continuous (never ending?) flow of air bubbles in the expelled brake fluid in the bleeding kit tube.
It seems as though air is getting into the system?
I can't see how though, the fluid reservoir is kept topped up during the bleed process.
I am just about at the end of my tether, I don't know what else to do. Just about in tears through the frustration!

Any help very gratefully received.
Much thanks in advance
Andy