Strange Growth (camillia)

I'd imagine its a gall of some kind, not sure which creature would have caused it. It's huge, isn't it - I will have a trawl through the book to see if I can find more details. I take it you have removed the affected branch?

Well, no further info available from my books here. Hope it's the only one, but they don't usually kill the plant, it's just the plant's reaction to whatever has invaded it. Maybe someone else will know more exactly what caused it.

could be a type of spider

It is a camellia gall, Bamboo ,according to my book.'The creamy white surface is made up of fungal spores so gall should be removed and destroyed asap.
Caused by damp weather and spread by rain splash and insects.'
'The overall health of the plant should not be affected.Only one or two per plant they appear in place of a leaf.
Keep a look out for future galls and remove before spores have chance to develop ' At least the plant will be ok Topbanna so hope this has reassured you :))

cool you learn something every day