I think Robert Swindells portrays the charcter of shelter as insane you can prove this because Shelter says in the book “Good morning shelter, I say to the bathroom mirror”.This shows he speaks to himself and, that he wants to play the charcter of Shelter correctly so, that he can convince homeless people that he is a “do-gooder”.
I also think that Robert Swindells wants us to feel empathy for shelter because his been “discharged on medical grounds” from the army, which have left him to fend for himself on the streets of london so, its really the armys fault that Shelter is mudering homeless people.
Shelter has many habits his picked up from the army, for example he plans things “I have aquired a cat, theres something reassuring about a home with a cat in”.This shows that Shelter is planning to become a “do-gooder” to trick homeless people into thinking its safe at his houe.
Another habit that Shelter has picked up out of the army is the way he speaks, for example he says stuff like “by golly”, “riff-raff” or “its a case of wait for it you 'orrible little man.This shows that he speak very old fashioned and he picks up some of his direlect from the army.
In conclusion I think Robert Swindells portrays Shelter as a mixed up charcter with many issues including paranoia and being insane but still making us fill empathy for him despite the fact he is a brutal killer and a complete phsyco.