If it's an early flowering one, do it after flowering, otherwise Feb is the preferred month.
https://www.rhs.org.uk/plants/clematis/pruning-guide
Then again, it's so mild in London, now probably isn't a terrible time.
Oh interesting, assumed it was group two but looks like it is group one (Montana) so will wait
We had a massive montana. I always pruned it after flowering when it started to go completely wild, sending out shoots everywhere.
@branwen started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
If it's an early flowering one, do it after flowering, otherwise Feb is the preferred month.
https://www.rhs.org.uk/plants/clematis/pruning-guide
Then again, it's so mild in London, now probably isn't a terrible time.