Law & Order: UK S02E06 - Honour Bound

Ronnie agrees to help his old friend and partner, DS Jimmy Valentine in an undercover drug sting, but a gun is pulled and someone ends up dead. What appears to be a tragic mistake is then investigated by internal affairs, and DS Devlin fears Jimmy is not all he seems. As they push for the truth the spotlight turns on Ronnie and his dark past as a functioning alcoholic when a ten year old drug case was left with a large quantity of missing heroin. The evidence is stacking up and James and Alesha battle Valentine's barrister, Evelyn Wyndham to bring enough evidence to court, and Ronnie's the key... but Ronnie refuses to testify.