Leaves still look dark green and shiny but have suddenly started to drop off plant. This year plant, which is in a large patio pot, has had many more flowers than last year and looked a picture!
I'm sorry your Camelia is dropping leaves! Is your plant getting a lot more sun than last year? It may be suffering from sunscald. Or if it has been repotted, the new soil may not be agreeing with it (Camelias need acidic soil and good drainage).
These articles may help you:
A Camellia will lose some leaves naturally each Spring. Look for signs of new leaves coming in.
Cold weather can also cause leaf drop.
Poor drainage can also starve the plants roots of oxygen, causing leaf drop.
More serious pest and disease issues are discussed in the article below.