Mine in pots are both 'leggy, so I share your concerns re strength. I read that they respond well to severe pruning, but I'm reluctant to try on both, so one will get slashed back next April, after danger from frost has passed. Presumably, where you are, you can do that sort of thing a little earlier in the year, i.e. just as the new growth starts, so the plant grows vigorously away without realising it's been pruned. Phil

If it is fruit bearing size, I would prune it right after harvesting the fruit in spring. That gives you your best chance of not interrupting the fruiting cycle. However, a hefty enough pruning can still stop fruiting for 1-3 years.

I had a couple of very old specimens in my garden in northern Spain and pruned them as Tugbrethil says. I opened out the centre and took off weakened branches. The following year they produced masses of flowers in December and then much larger fruits in Spring. Very easy to propagate too.