The character played by James Coburn in the Great Escape is based on which person?

Bram van der Stok -- In the 1963 film The Great Escape, he was composited into the character of Sedgwick, played by James Coburn.

James Coburn (Sedgewick, the Manufacturer). An amalgamation of Al Hake, compass maker, and Johnny Travis, the real manufacturer. Coburn also reaches safety, and this, the third successful escaper, was in real life Bob van der Stok, who escaped into Holland and Belgium, then over the Pyrenees into Spain and Gibraltar. The scene where Sedgewick produces a large suitcase which has to go down the tunnel is true, but the real escaper in this case was Tim Walenn, the real-life forger. Hake and Walenn were murdered; Travis did not escape.

https://en.wikipedia.org/wiki/The_Great_Escape_(film)
https://en.wikipedia.org/wiki/Bram_van_der_Stok

James Coburn played Flying Officer Louis Sedgwick "The Manufacturer."

An amalgamation of Al Hake, compass maker, and Johnny Travis, the real manufacturer. Coburn also reaches safety, and this, the third successful escaper, was in real life Bob van der Stok, who escaped into Holland and Belgium, then over the Pyrenees into Spain and Gibraltar. The scene where Sedgewick produces a large suitcase which has to go down the tunnel is true, but the real escaper in this case was Tim Walenn, the real-life forger. Hake and Walenn were murdered; Travis did not escape.

http://robdavistelford.co.uk/webspace/gt_esc/movie.html