This flown cover was one of the last air mail covers flown by Smithy. It comes from the collection of Phil Vabre who has catalogued it thus:

Cover flown on Kingsford Smith's last flight, an England-Australia record attempt in Lockheed Altair G-ADUS "Lady Southern Cross". The flight was abandoned at Brindisi after encountering violent storms over the Adriatic which damaged the aircraft. Aircraft and crew returned to England 24 Oct and set out again on November 6. The mails were re-posted but did not reach the aircraft in time and so were left behind. Kingsford Smith, mechanic Tommy Pethybridge and the "Lady Southern Cross" were subsequently lost without trace off the Burma coast. Cover first postmarked on 2d red KGV at Darwin 3OC35 before being taken to London (addressed to Smithy there) by Beau Sheil (Smithy's PA) by KLM and Imperial Airways. Cover again posted to Smithy in London c/o Vacuum Oil Co, postmarked London SW1 6.15PM 18OCT 1935 on perforated 1 1/2d brown KGV. Readdressed to Smithy at the Sydney Morning Herald, Sydney for the flight out. For the second attempt, cover posted again addressed to Smithy c/o the Post Office at Hythe, postmarked London ? 6.15PM 5 NO 35, again on perf 1 1/2d brown KGV. Backstamped on arrival at Hythe 9-AM 6 NO 35. Includes a large red cachet on reverse giving an outline of the story, numbering the cover 17 of 49, and signed by Beau Sheil. Eu ref 545

Source: Phil Vabre Collection