Is your acer in a pot or in the ground and has the weather been dry where you live? Or is the acer in a very windy position?

The acer is in the ground, I'm just on the border of London and Essex so it's been mainly wet and the wind has not been unusual. This did happen last year but stopped after I pruned the tree but not this time

Acers should only be pruned in late autumn when the sap is down, otherwise they bleed. You say the wind has not been unusually but is the t red planted in a spot where the wind blows through, if so then you will have shrivelled leaves every year as acers hate wind.

Thank you. I guess that will be the answer. Unfortunately it's now to late to change the position.

Depends on how long you've had it in that position, if it is only a couple of years you could try moving in late autumn provided you take a big enough root ball and have the new planting hole all prepared before you lift.

Too late for that I'm afraid because the tree is now at least ten years old so is very well established in it's position.

Thank you for your help

Is there any way you can create some sort of windbreak to protect your acer?

Unfortunately no

Pity.