 Complete the following phrase:  On 19 June 1915, after Churchill had been replaced as First Lord by Arthur Balfour, a conference was held at the Admiralty to consider all airship development. At that time the non-rigid airship programme was proving to be successful, and at this meeting it was agreed to expand the non-rigid programme and also to resume construction of HMA No.9. However, resumption of work was delayed by the necessity to retrieve Pratt and Wallis who had enlisted in the Army when construction was cancelled. Final erection of the ship began in the autumn of that year, but there were delays in obtaining flax from Ireland to make nets for the gasbags following the 