He comments that "putting the bars at the driver's sides made it easy to steer and felt very natural".[26] A prototype was presented to 63 families in the A, B, C1 and C2 demographic groups in suburban and town environments to determine that the controls were correctly positioned; this was the only external research carried out on the C5.[2] In the autumn of 1983,[20] Wills brought in Lotus Cars to finish the vehicle's detailing, build prototypes and test rigs, carry out testing and take forward the programme to production.[3] The development of the C5 took place over 19 months in conditions of great secrecy, with testing carried out at the Motor Industry Research Association's proving ground in Leicestershire.[4]