" I was prompted to have a look on wiki at Gallipoli. It doesn't make nice reading for the "they were well-led" brigade."

Couldn't agree more Steve and I have stated so before on this thread - however if you wish to examine the worst case and example of bad leadership in the British Army go no further than Townshend in Mesopotamia But taking your example Gallipoli - it actually came very, very close to being a complete and utter success once during the naval assault on the Dardanelles and second when the British landed at Suvla, had the British troops had an aggressive and energetic Commander the Turks would have been cut off with no hope of relief or supply in 24 hours.

But those examples do not reflect the prevailing capabilities and performance of British, Commonwealth and Empire forces commanders from 1915 onward so the point now agreed upon by modern historians and described by Keith A as follows still holds good:

In general compared to the armies of other combatant powers the British Army was well led

Douglas from becoming Commander of the 1st Army in 1915 consistently gave his German enemy severe problems and that they acknowledged that with their dispositions when facing British troops.