Complex sentence: Recreating 11 miles between Wareham and Swanage, by Spring 2015, (Forming one of only a small number of heritage railways to operate a whole branch in it's original form of entirety).
Split into simpler sentences: Recreating 11 miles between Wareham and Swanage, by Spring 2015. Once running all the way from Wareham to Swanage the ex-Southern branch line will once again run at a total of 11 miles in length, (making this a whole branch in it's original form of entirety).