Last night I found and watched this! - 'From Sea to Sky' - The Flying Boats in Australia
http://youtube.com/watch?v=305OVtcvJn8 It even includes a brief bit of footage showing a typewriter being used on board to type up menu's! So now I know these were probably 'standard issue' typewriters from Imperial Airways! Maybe grandfather had the one on his 'boat' modified to add another • so he didn't need to come out of 'shift lock' in order to type frequent lines (on forms?).
The Last African Flying Boat (1993) doco was also excellent.
However there is a lot more to it all than that it seems.
Here is an amazing talk given about early air mail services. Seems
Imperial was running routes in Middle East from 1920s into 1930s Also:
http://www.bluegrassairlines.com/operations/imperial_airways/Eastern_%20Route.htm It seems that air routes from Cairo (avoiding desert) to India, and Cairo to South Africa, were surveyed between 1925 and 1930. My grandfather may have been involved with some of those. I know he spent time in Singapore, Cairo and East Africa.
Wish I still had the envelope addressed to him at 'The Club', Singapore, to get a date. Such a different era! And his RAF badge thingy.
research:
http://www.century-of-flight.net/Aviation%20history/coming%20of%20age/imperial%20airways.htmhttp://www.pprune.org/archive/index.php/t-491429.htmlhttp://paleofuture.gizmodo.com/what-international-air-travel-was-like-in-the-1930s-1471258414