FIREARMS ACT 1968
IT IS AN OFFENCE FOR SOMEONE WHO IS PROHIBITED BY SECTION 21 OF THE FIREARMS ACT 1968 TO HAVE A FIREARM OR AMMUNITION IN THEIR POSSESSION AT ANY TIME.

Section 21

Applies to anyone who has been sentenced to imprisonment or to youth custody or detention in a young offender’s institution for three months or more.

The period for which they are prohibited depends on the length of the original sentence – not the actual time served. 
If the sentence was for more than three years the prohibition is for life.

If the sentence was for three months or more but less than three years, the prohibition lasts for five years from the date of their release.
These periods apply even if the sentence was suspended in which case the prohibition applies from the second day after sentence.

It is an offence for a person to transfer, let or hire, give or lend a firearm or ammunition to someone he/she knows, or has reasonable grounds for believing, to be prohibited by section 21.