MENS REA

A scenario: M, a drug supplier supplies T, the buyer with heroin every month. M's supplies always come from a particular source. At the last supply, M was informed of the  pure nature of the heroin. M did not inform T of the pure nature and T consumes the normal dosage and dies. M argues that though he supplied the heroin, he did not force T to take it. Will M be held responsible for T's death? Can it be said that M was reckless or negligent?
Recklessness is a subjective form of mens rea which means looking at what the actual defendant was thinking or what the magistrates or jury believe the defendant was thinking. The defendant must always be aware of the risk in order to satisfy this test of recklessness.M would not have wanted T dead because that will mean losing one customer.
Was M negligent? This test can subsist where a duty of care is owed and this can arise where there is a relationship existing between the parties involved. Can it be said that there exists a relationship between M and T, whether that of contractual relationship or that they were neighbours?
Possession of heroin is an offence under the Act(Offences Against The Person Act 1861) but administration of drugs unto oneself is not an offence. It can be argued that being in possession of heroin did not kill T but the taking of the heroin and the issue in question is the death of T.Therefore it can be said that M cannot be held responsible. See the case of Kennedy [2005] EWCA Crim 685.
The fact that informing T of the pure nature of the heroin MIGHT have made a difference, should it be thrown out?