Although a very few of the later larger locomotives were fitted with mechanical stokers almost all locomotives on British Railways were fired by hand. The railway unions had an agreement with British Railways that the maximum amount of coal a single fireman would be expected to shovel into the firebox was 3,000 pounds (about a ton and a third) per hour. This met all usual requirements on Britain’s railways and in fact most duties involved considerably less than that.
Large passenger express locomotives had a tender capacity of about eight to ten tons of coal and about 4,500 - 5,000 gallons of water. A crack express loco running from London to either Edinburgh or Glasgow would consume about eight tons of coal on the run but would need to replenish the water supply at least four or five times on a four hundred mile run. This was achieved without stopping by means of a scoop lowered from the tender (a task undertaken by the fireman) into a water trough laid between the rails.
As well as feeding the fire (which had to be done almost continuously on a fast run) the fireman was also responsible for keeping the tender full of water (see above), for monitoring the steam pressure in the boiler, for keeping the boiler water level topped up (by means of injectors from the tender) and for helping the driver “sight” signals in tricky conditions.
As heathfield mentions, the East Coast route operated the longest daily non-stop steam powered run in the world from London to Edinburgh with trains taking about six and a half hours to make the 393 mile run. A spare crew would travel in the first coach and would relieve the original crew at the half way point by means of a corridor tender, designed by Sir Nigel Gresley. Here’s a nice picture of such a tender:
http://www.train-phot...cture/number11900.asp
You can see flexible corridor connection which would mate to the first coach, and the round window which would provide a bit of daylight for the crew as they squeezed through the passageway (which was only eighteen inches wide and five feet high).
Firing an express locomotive was an extremely demanding job. The footplates were semi open and in the winter the crew would find themselves with roasting fronts and freezing backs (though fireman will tell you they preferred that to the summer when all round temperatures would be ferocious). To gain an idea of the demands of the job pay a visit to a heritage railway and see the effort needed by the fireman to fire a loco on a short run of ten miles or so at a steady twenty miles an hour. Then imagine the same job being done on a swaying footplate at speeds up to 100mph for four or five hours at a stretch. They were indeed a different breed!