Complex sentence: ML contracted Cammell Laird of Birkenhead to build two smaller vessels of 1,800 tons and these were commissioned in 1952, named the "Manchester Pioneer" and "Explorer"; these were joined by the secondhand 1,400-ton "Manchester Prospector".
Split into simpler sentences: ML contracted Cammell Laird of Birkenhead to build two smaller vessels of 1,800 tons and these were commissioned in 1952, named the "Manchester Pioneer" and "Explorer". They were joined by the secondhand 1,400-ton "Manchester Prospector".