He is 16 and lives in the UK.
I don't think he can buy a gun just yet.
And even if he could get his hands on one, it would be illegal to wair/use it.
Although I might be wrong ofcourse.
You are indeed correct. It is completely illegal to possess a gun unless you have a hunting lisence or a police trained lisence.
Aikido is useful against weapons to unarmed situations. In the UK most youths on the streets are drunk, drugged up or so angry they are disorientated. Aikido I feel is an art that protects yourself from being stabbed and also makes sure that the attacker won't land up in casulty. They have enough problems already.