Lemon tree

my lemon tree needs help I read somewhere that leaves turning pale and fruits turning black and falling can be due to different problems. I enclosed a pic of my lemon tree, if anybody knows what's happening to my lemon tree please advise me on a course of action Thanks
(South of England)
Giuseppe

 

Not sure, but looks like chlorosis, nitrgen deficiency

 

I agree, but here is a link to identification of deficiencies.

http://edis.ifas.ufl.edu/CH142

-- Skeet

 

thank you very much for your reply. I thought at first that was ion deficiency but judging from the picture from your link I have to agree to the fact that may be chlorosis. I will take a picture of a single leave and show it to you.
Thanks