Although difficulties had been experienced for many years in preparing initial estimates for major defence development projects and in the control of subsequent expenditure, they did not become a matter of serious concern until the second half of the 1950's. Then, at a time when the Government was seeking to stabilise defence expenditure, a series of cases came to light where final costs were, or seemed likely to be, substantially higher than the estimates at which they were first approved. Some of these projects attracted the attention of the Public Accounts Committee and led to considerable public criticism.