Mk1 Escort no brakes

My old brown mk1 is suffering with a really soft brake pedal. Real soft, as in it goes to the floor and only just slows things up.
 
I pulled all the wheels off and checked calipers and rear wheel cylinders, checked lines and fittings. No leaks anywhere. The reservoir is still full too, and there is no leaks from the end of the master cylinder either.
 
Does that point to the master cylinder being stuffed? Or should I try bleeding the system first before assuming a bung master cylinder?

Thanks SFE. I'll drag the wife or one of the kids down to the shed and get them to do some stomping to see what is happening.

How old is the fluid in your system? If its been in for yonks will not be as effective. If your going to do a bit of " bleeding " completely bleed the entire system and replace with new fluid. Len

If you can get a  helper and have some catch cans for 2 wheels, open the bleed valves in pairs, front and rear and pump the whole contents of the master cyl through a couple of times to ensure all the old fluid is purged and hopefully all the air.  Does a Mk 1 have a proportioning valve for the front and rear circuit like the Mk2? If the rubbers are perished maybe it is getting stuck? Len