This sturdily-built hand-operated planing machine with a 4-spoke capstan operating hand driving a 30" x 10" table could have been at any time from the late 1800 to the 1930s--when such machines were still illustrated in the hard-bound catalogues of the larger machine-tool merchants. However, judging by the over-size nuts, open bevel gears and the table drive gear with a shoulder it's almost certainly late Victorian. Although hand-operated the machine would have been capable of very useful work - even today they are a sought-after tool--and able to mount odd-shaped castings and other difficult workpieces with ease. All planers also have the advantage of being remarkably compact for their enormous machining capacity.
Brittain are a long-forgotten make and if any reader has details of the Company  the writer would be interested to hear from them.