Has a dog been spraying it?

It looks like mine when i don't water it enough.
Also, how deep is that planter that you've got it in ?

Because these are such thirsty vines that potted plant will need a hosepipe on it, on a slow-medium speed for 5 minutes a couple of times a week, using a watering can won't get enough prolonged moisture to the base of the rootball.

The roots of clems go down at least 12", is that planter/pot deep enough to allow that ?

Hi Mark I am so glad you asked this question as my clematis is doing the same. My one is planted near to my little tin bath pond up against the fence. Think I'll have to move mine if it isn't getting enough water. I do hope your recovers

When planting them against fences and walls the rootball needs to be at least 18" away from them or the shelter from the structure doesn't allow for enough moisture into the soil (from rain or manual watering).

Always angle to plant in towards the wall/fence.
This goes for roses too.

On the subject of watering clematis, does anyone know the extent to which the roots spread out from the stem?

I would say its short of water.

Thank you Louise1 I'm sure me and Mark61 will heed your advise

Mine did that a few weeks ago....the whole thing looked dead. Chopped it off about 6 inches above ground level and have been watering it and it's sending out lots of new buds so at least it's not totally dead and hopefully will be ok next year!

But the very same thing will happen, Gaia01 if the plant gets dehydrated again - all this new growth will do exactly the same thing.
These plants are vines (like grapes) and as such have massive water needs.

Hi all thankyou for your comments.I have now added a blog showing the new planter i have built for my clematis now.Hopefully it will spring back into life.:))))