United Kingdom, March 7 -- Hero Fiennes Tiffin felt he had to prove himself as an actor to his uncle Joseph Fiennes on Young Sherlock.

The 28-year-old star questioned if his performance of a young version of Arthur Conan Doyle's fictional detective was good enough when 55-year-old Joseph - who plays his onscreen dad, Silas Holmes - rocked up on the set of 57-year-old Guy Ritchie's Amazon Prime Video series.

Hero told People: "At the start of any show, I've got a bit of imposter syndrome. I'm like, 'Why are they trusting me to do this? It's a massive role.' The word daunting is definitely one I'd use.

"And then you get those nerves out the way, and you really start to enjoy it. And then Joe comes in, and you're like, 'Oh, I'm back to th...