Complex sentence: During its working life the class could be found all over the NER system working on suburban lines and country branch lines but during their life with the LNER they were mostly kept around Tyneside, Teesside, Hull and Leeds where they handled lightweight traffic.
Split into simpler sentences: During its working life the class could be found all over the NER system working on suburban lines and country branch lines. During their life with the LNER they were mostly kept around Tyneside, Teesside, Hull and Leeds where they handled lightweight traffic.