The calculated distance (air line) between Shaftesbury and Southend-on-Sea is approximately 131 miles respectively 211 kilometers.
By car or train, the actual journey to Southend-on-Sea is certainly longer, as only the direct route (as the crow flies) between Shaftesbury and Southend-on-Sea has been calculated here.
Air line (approximately)
211 kilometers
114 nautical miles