Sociopathy, or Anti-Social/Dissocial Personality Disorder is loosely defined but is described by the World Health Organisation and the American Psychiatric Association as including the following behavourial indications -
Callous unconcern for the feelings of others;
Gross and persistent attitude of irresponsibility and disregard for social norms, rules, and obligations;
Impulsiveness or failure to plan ahead;
Irritability and aggressiveness;
Reckless disregard for safety of self or others;
Consistent irresponsibility, repeated failure to sustain consistent work behavior or honor financial obligations;
Lack of remorse, incapacity to experience guilt being indifferent to or rationalising having hurt, mistreated, or stolen from another;
Incapacity to maintain enduring relationships, though having no difficulty in establishing them;
Prone to blame others, or to offer plausible rationalisations, for the behavior that has brought the person into conflict with society.
(Basically, you could say that the individual lacks a conscience.)
If someone exhibits three or more of these characteristics then further clinical examination would follow to establish the level of sociopathy present. There is apparently a genetic element so investigations would have to be made into family background too. It cannot be 'cured' but treatment with psychoactive drugs and cognitive therapy can succesfully manage the condition.
In the time since he's been in the public eye i.e. since the banking crisis of 2007/ 2008 and up to date, Bob Diamond has shown a lack of remorse, callous unconcern for others, deception, irritability and aggressiveness, consistent irresponsibility, an incapacity to experience guilt, and has tended to blame others for his dysfunctional behaviour. I reckon this makes him a suitable case for further investigation at least, and if his employers at Barclays Bank had any sense of compassion they would put him on extended sick leave. If he or his employers deny that Mr Diamond is suffering from this condition then we must conclude that his anti-social behaviour is deliberate, and despite his conscience, in which case he should be fired and investigated for fraud.