The final decision was in his favour, allowing him to proceed with the project.

in 是介词，表示"在...方面"或"处于某种状态"。 his 是代词 he 的所有格形式，表示"他的"。 favour 是名词，意思是"偏爱、支持、好处"。 in his favour 这个短语表示"对他有利"，指决定或结果偏向于支持他。