Complex sentence: Drummond authorised a further batch of ten locomotives from 1897 to 1898 after being impressed with the performance of the class, whilst a further, and final, batch of ten was ordered in 1900.
Split into simpler sentences: Drummond authorised a further batch of ten locomotives during the period 1897 to 1898 after being impressed with the performance of the class. A further, and final, batch of ten was ordered in 1900.