The calculated distance (air line) between Southend-on-Sea and Walthamstow is approximately 32 miles respectively 51 kilometers.
By car or train, the actual journey to Walthamstow is certainly longer, as only the direct route (as the crow flies) between Southend-on-Sea and Walthamstow has been calculated here.
Air line (approximately)
51 kilometers
28 nautical miles