There you go you see,that's something else I've learned today......not that it'll do me a blind bit of good,but learning all the same
I would add for your information Baza that LMSR engines did not have smoke deflectors fitted originally, and only the 4-6-2 Pacific Turbomotive class engine had them fitted in 1939. Thereafter the previously streamlined 4-6-2 Pacific Duchess class locomotives had them fitted after being rebuilt, but that was in the early days of British Railways from 1948. From that time the British Railways large 'Standard' engines, such as the 4-6-2's and 2-10-0 9F's had large deflectors as an integral part of the original design.
The GWR never adopted the smoke deflectors, but the SR did, with experiments by their CME, R.E. Maunsell on some classes of engines from 1927. Later SR 4-6-2 Merchant Navy and West Country / Battle of Britain class engines designed by Oliver Bulleid were streamlined, as engineering practice favoured during the late 1930's, and built from 1941 onwards with various versions of built in deflectors. Like the LMS streamliners, British Rail rebuilt these SR streamliners from 1956 onwards with large smoke deflectors. Other SR 4-6-0 classes of passenger and freight engines were also blessed with deflectors by British Railways.
Apart from the previously described LNER A3's that eventually had deflectors fitted, Gresley's A4's were streamlined so did not need them, and as they were kept in streamlined form by BR, never had them fitted. Only Gresley's six 2-8-2 P2 class locomotives were built with integral deflectors from new in 1934. Gresley's also fitted deflectors to his two 2-8-2 P2 Mikados engines. His experimental 4-6-4 high pressure engine, No1000, built in 1929 also had a streamlined form with integral deflectors.
I hope that is all of interest