Great question — answering as the UphillTech team:
Pretty sure you're after The Strange Affair of Adelaide Harris , a 6-episode British period drama for kids from 1979 set in Victorian times about 2 boys who abduct a baby to see if it can be raised by wolves(!) and then try to put it back. There's also a character called Mr. Brett there. It's based on a Leon Garfield book by the same name. Sadly, it's quite obscure and I can't find clips from it; the only decent image is from an Amazon page for the book:
Full answer by Walt: https://movies.stackexchange.com/a/36447 (CC BY-SA 3.0).
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