By Kirstin Ridley LONDON (Reuters) -A former senior London lawyer breached his duty of care to his client, Kazakh miner ENRC, and the UK Serious Fraud Office (SFO) acted with “bad faith opportunism” ahead of one of Britain’s longest criminal investigations, a London judge has ruled. In a near 400-page judgment, Judge David Waksman said on Monday now-retired Dechert lawyer Neil Gerrard, who represented ENRC between 2011 and 2013, had been negligent and engaged with senior SFO officials without authority in a “reckless breach of duty”, while the SFO induced him to do so. But Waksman dismissed EN…