Sounds as though it needs a thorough watering, Dave. You may be able to save it with loads of water now, and it would be a good idea to make a well in the soil all around the base of the tree to water into, so that it doesn't all run away. Keep on watering it as often as possible, and take off all the dead 'leaves'. We had that very dry, hot spell earlier in the year (hard to remember now after all the rain!), but that's probably when the trouble started. Hope you can save it. Annie (Cumbria)