Groaning noise

Dan

London

Was driving the Ambassador yesterday (my 28,000 mile black VDP pictured on the start page) when after an hour`s drive there began to be a rhythmic groaning noise from the front which got noisier the slower the car went. I'm pretty sure it's to do with the front brakes or drive shaft gaiters because it made a ""rubber being squeezed"" grating- type noise and seemed to get quieter when I put the brakes on. When I looked under the car I could see nothing amiss. Any experiences / ideas ? Thanks Dan