Hi Harry,
If you are still on the register the likely hood is that your PPU officer will place a green notice on your passport, and when you go through passport control in Egypt it will flag and they will most likely ask you a lot of questions as to if they let you in then thats the million dollar question 

If you are no longer on the register then do not even think of disclosing, the Egyptian authorities do not have access to the Police national computer so will never know.

Hope this helps 

I have a friend in Egypt I want to visit and I have seen a sample  visa form which, at the bottom says : Applicants with previous convictions should declare their convictions below or on a separate sheet.

Now I have a spent conviction so am considering not admitting it as it is spent. 

Does anyone know if this will cause me a problem?