As Barry suffered from ... Bob may be liable under S.20 Offences Against the Person Act 1981. This is unlawful and malicious wounding or inflicting grievous bodily harm (GBH).
To amount to a wound both of the layers of the skin must be broken, internal bleeding is insufficient.
GBH is defined as really serious or simply serious harm. The ordinary man in the street is likely to regard GBH as serious harm.