The NBR K Class is a class of 4-4-0 steam locomotive of the North British Railway. The first batch (later LNER Class D26) was designed by Matthew Holmes in 1902 for express passenger work. Three more batches (later LNER Classes D32, D33, and D34) were designed by William P. Reid for mixed traffic work. This included perishable goods, such as fish from Mallaig and Aberdeen. 

The D34 locomotives, commonly known as Glen Class, were built with superheaters. The LNER later fitted superheaters to all D26, D32, and D33 engines as well. All engines of the K class are sometimes known as Glen Class, although the designation is strictly reserved to the fourth (D34) batch.

Ten engines were built in 1913 and a further twenty-two engines were built between 1917 and 1920. Withdrawals began in 1946 and all the D34s had been withdrawn by 1961. One has been preserved.