In article , K
writes

The thing in the picture with the vaguely holly-like leaves and the
fruits setting is Mahonia aquifolia. Attractive purple fruits, good
autumn colour, fragrant yellow flowers in spring.

It can take over a bed a bit Kay, it's easy to move a bit by yanking out
some of the other stems as they should be rooted in the ground. I find I
have to prune mine quite a bit as they go sideways and start to
encompass an enormous width of ground!On the other hand i don't think it
will necessarily strangle the deutzia but it will make pruning the
deutzia more tricky if the Mahonia is allowed to get too tall.
Also a swine if it gets ground elder amongst its stems as in one of my
beds!
--
Janet Tweedy
Dalmatian Telegraph
http://www.lancedal.demon.co.uk