The  Alfred Hitchcock " Miniatures and matte painting"

Under Capricorn (1949)

No credited FX person.
Matte painting: Unknown.
It was filmed at MGM British Studios, so probably a British matte painter.
At 1949 there were not much matte painters credited at Britain. Walter Percy Day was at Shepperton, Peter Ellenshaw was working for Disney "Treasure island".
Albert Whitlock made his first matte painting at that year for "The bad lord Byron" and according to him he didn´t paint his first matte in colour until 1953 for "The Seekers".
Les Bowie was at Pinewood matte department. And at Shepperton matte department was Albert Jullion and probably some others, under Percy Day supervision.
There wero two other credited matte painters working at 1949, Ivor Beddoes and Joseph Natanson whom had alredy worked together with Les Bowie for "The red shoes".
Obviously there were some other British matte painters working uncredited.