Complex sentence: The first six locomotives were built by BR at Eastleigh works in 1962 and were numbered E6001-E6006 and classified as type Class JA. With the introduction of TOPS in 1968 they were to have been classified as Class 72, to differentiate from the later built units.
Split into simpler sentences: The first six locomotives were built by BR at Eastleigh works in 1962 and were numbered E6001-E6006. Under the introduction of TOPS in 1968 they were to have been classified as Class 72, to differentiate from the later built units.