Despite his aggressive nature, Phil is a likeable character with whom the audience can empathise.
His quick wit and energetic humour make him engaging, and his rare moments of vulnerability and honesty give us an understanding of his less appealing traits. This helps the audience to relate to him.
An example of this is when he describes his father’s inability to cope with his mother’s mental illness:
Course, he's hopeless... thinks it's like diptheria or something.
We see his kind nature when he asks Lucille to The Staffie on Hector’s behalf, instead of taking her himself. The love and devotion he has for his ill mother is admirable and he is angered by the mistreatment of her:
Medicine? Forty bennies crushed up in their cornflakes before they frogmarch them down to ‘Relaxation Classes’, then it’s back up to Cellblock Eleven.
Only in his most honest moments do we see Phil's true vulnerability. A thread of doubt through his dialogue and actions leaves both Phil and the audience wondering if he too may be susceptible to mental illness. He asks Spanky:
D'you think going off your head's catching?
His increasingly erratic behaviour could be seen as indicative of mental illness.