they look like quince fruits.

is it the first time you have seen fruit on your tree. what is the flower like?

Hi, welcome to GoY, I agree with Sbg, the fruits look to be almost spherical, if they are, then it's probably Cydonia oblonga 'maliformis' Derek.

If that's what they are try slicing one and adding it when you make an apple pie or crumble - you only need one to add some real zing!

Feijoa Sellowiana the Pineapple Guava. Is the shrub evergreen? Google the name and have a look at the flowers, that should give the answer.

Never heard of that so looked it up. This link shows the flowers - very pretty!
https://www.victoriananursery.co.uk/Pineapple_Guavas/

Send us a taste if that's what it is!

Hi, yes Jimmy's right, should have known that by the 'Maltese cross' shape on the inside, must be getting old, memory going a bit ?, Derek.