Two spot ladybird

This attractive beetle was sitting quietly in a Japanese anemone until I came along and spooked it.
 
When reading up about it, I came across a way of identifying it and differentiating it from the 10 spot ladybird. 
 
Quote. 
"The only likely species that may cause confusion is the 10-spot ladybird, which is a similar size and variable in pattern. However, 2-spot ladybirds have black legs, while 10-spot ladybirds have orange legs."
 
I am now going to go away and think about this for a while....taking into account that there may be an easier way to differentiate the two than examine the colour of the legs.
 
Could it be the number of spots?