Best to remove your email address from your question - this is a public site and that means anyone and everyone in the world can see it.
Is this 'castor oil plant' outside in the garden, in a pot outside, or in a conservatory? Ricinus, which is castor oil plant, is a tender annual in this country - the one which grows outside year round is a different plant called Fatsia japonica. How long have you had your plant and again, is it in the ground or a pot?

plant is about 9 years old and outside in the garden
tom

Fatsia japonica then. If there's no obvious signs of infestation or infection, most likely its the return to colder temperatures during April after such a warm March. These plants do lose leaves all year round - they usually go yellow before turning brown and crispy. Leave it alone for the time being - when growth starts again as the weather warms up, if you need to prune any dead or tatty parts off, do it end of May beginning of June.

thanks you for your prompt reply