The North British Atlantic, later known as NBR Class H, and then as LNER Class C11 was a class of 4-4-2 steam locomotive of the North British Railway. The class was designed by William P. Reid, Locomotive Superintendent of the NBR, and entered service under his direction. They were the heaviest, longest, and most powerful (by tractive effort) locomotives ever employed on the North British Railway. The NBR Class I, later known as LNER Class C10, was a temporary designation of some engines in this class (see below).