In 2009 Cameron started by joining what became the ECR (eurosceptic) group in order to appease the sceptics in his party and in one step alienated those we want to work with for a better EU.
The result is that not only was any attempt to negotiate the terms of our membership doomed, but also the Brexit case is based on an unrealistic view of our potential position in the EU once we have a PM with the courage to take a lead in Europe.