The five-year-old lost his unbeaten record when pulled up in the Albert Bartlett Novices' Hurdle over three miles at the Cheltenham Festival, and starts life in his new discipline over the intermediate trip of two miles and almost three furlongs.
But he faces a far from straightforward task, as up against him is Nicky Henderson-trained stablemate Angels Breath, Nick Gifford's The Mighty Don - who is the highest-rated runner of the four - and Kim Bailey's First Flow.
Owned by JP McManus, Birchdale will be ridden by Barry Geraghty, who said: "He's one to look forward to, he's schooled nicely at Nicky's, so fingers crossed.
"When results don't work out as you'd like (at Cheltenham) you tend to think you've got it wrong.
"The time before he was in the process of running a massive race, even before Brewin'upastorm fell, so we know he's good.
"Ascot is the best track to start off at, so I'm looking forward to it."
First Flow was a smart novice hurdler two seasons back, but because of the quick ground that prevailed for much of the last campaign, he was only out once.
He has already run this term, though, when finishing second to 2018 Supreme Novices' Hurdle winner Summerville Boy on his chasing bow at Uttoxeter.
However, that performance was notable for the fact he jumped markedly right at some fences, so it is no surprise to see him switch to a right-handed track.
"He did favour going right in all his hurdle races, but we wanted to start him off at Uttoxeter," said Bailey.
"Hence we're going right-handed now. It was a nice run apart from that, but we could do with some rain."
Bailey also has an interest in a later race, the Join Kim Bailey 'Introductory' Hurdle.
"I'll be doing my best to win it with Mr Grey Sky, he was two from two in bumpers and looks a nice horse," said Bailey.
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