After the armistice he returned to Birmingham and tried to find work as a cartoonist. He sold two cartoons to the Bystander in 1919 but was unable to secure a permanent position. Later that year he embarked on a professional stage career. Under the tutelage of actor-manager Nigel Playfair, he worked as an actor, set designer and builder, "stage director" (akin to a stage manager) and director. In 1922, while with Playfair, he met Doris Zinkeisen. They were considered a couple for some two years, despite Whale's living as an openly gay man. They were reportedly engaged in 1924, but by 1925 the engagement was off.  In 1928 Whale was offered the opportunity to direct two private performances of R.C. Sherriff's then-unknown play Journey's End for the Incorporated Stage Society, a theatre society that mounted private Sunday performances of plays. Set over a four-day period in March 1918 in the trenches at Saint-Quentin, France, Journey's End gives a glimpse into the experiences of the officers of a British infantry company in World War I. The key conflict is between Capt. Stanhope, the company commander, and Lt. Raleigh, the brother of Stanhope's fiancee. Whale offered the part of Stanhope to the then barely known Laurence Olivier. Olivier initially declined the role, but after meeting the playwright agreed to take it on. Maurice Evans was cast as Raleigh. The play was well received and transferred to the Savoy Theatre in London's West End, opening on 21 January 1929. A young Colin Clive was now in the lead role, Olivier having accepted an offer to take the lead in a production of Beau Geste. The play was a tremendous success, with critics uniform and effusive in their praise and with audiences sometimes sitting in stunned silence following its conclusion only to burst into thunderous ovations. As Whale biographer James Curtis wrote, the play "managed to coalesce, at the right time and in the right manner, the impressions of a whole generation of men who were in the war and who had found it impossible, through words or deeds, to adequately express to their friends and families what the trenches had been like". After three weeks at the Savoy, Journey's End transferred to the Prince of Wales Theatre, where it ran for the next two years.  With the success of Journey's End at home, Broadway producer Gilbert Miller acquired the rights to mount a New York production with an all-British cast headed by Colin Keith-Johnston as Stanhope and Derek Williams as Raleigh. Whale also directed this version, which premiered at Henry Miller's Theatre on 22 March 1929. The play ran for over a year and cemented its reputation as the greatest play about World War I.

Answer this question "what was one of the plays that was a huge hit" by extracting the answer from the text above.
With the success of Journey's End at home,