Why did Michael Praed not play the main role in Robin of Sherwood season 3?

The actor had another job that was incompatible:

In reality, Praed hadn’t been reclaimed by Herne the Hunter but had taken a job on Broadway, making an eleventh-hour decision to quit Robin of Sherwood in order to play d’Artagnan in a revival of Rudolf Friml’s Three Musketeers musical.

Not the best of decisions, as it turned out:

Sadly, following a less than fulsome review in the New York Times, the show closed after just nine performances. That must have hurt?

“Obviously I wasn’t jumping for joy, but that’s the game,” he shrugs. “It’s ruinously expensive to put shows on on Broadway, musicals especially. There’s an awful lot at stake, and in those days you had to get the New York Times review. It just had to happen. If you didn’t get it, you closed. And we didn’t get it.”

But the kicker is why he'd made such a rash decision:

“When I was young, about 16 or 17,” he recalls, “I asked a very wise old lady, ‘If you could pass on something to my generation, what would that be?’ And she fixed me with her beautiful blue eyes – I can see her now, with her intense stare – and she grabbed my arm and held onto it, and she said, ‘Michael, in your lifetime, you’re going to have three opportunities. Picture them as a bird with feathers. And what you must do is grab onto those feathers, and hold on for dear life, regardless of what happens. And you’ll know. You’ll know.’”

A dramatic pause. “I thought she was out of her f***ing mind!” he laughs. “But she was serious. And when The Three Musketeers came along, I thought, this is one of those opportunities.”

Though the play's failure didn't bother him that much:

“I’ve always been a great believer in chance for consequences. Because, look, it tanked, and so you could say, ‘Well you kind of f***ed up there, didn’t you Praed? You left that big hit show to go and do that. What the hell were you thinking?’ But had it been a big hit and I’d won a Tony Award, you’d be saying a different thing. So the decision to do it wasn’t incorrect. It’s a fool’s errand to judge an experience that’s been negative as invalid. Just because that show didn’t work, that’s not life’s journey.

“Also, I now know what it feels like as a young man to open on Broadway. I’ll never forget, after opening night, sitting in my dressing room and taking it in. This mayhem that we’d been through – a producer died during rehearsals, they fired a director. Crazy shit happened on that show. I made my entrance from the back of the stalls… on a horse. It was crazy. And I remember thinking, whatever happens, it’s been fun.”

He went on of course to score a major role in one of the most popular dramas of those days:

If that experience was crazy shit, it was nothing compared to Praed’s next engagement on glossy US supersoap Dynasty, in which the former Michael Prince became Prince Michael, heir to the throne of the fictional Eastern European kingdom of Moldavia.