I'll start, if I may, by addressing fervent fans of the film - of which I am one - and assure them this new musical version is even better. For them, at least, this should give some measure of the achievement of Matthew Warchus's production.
For everyone else, Groundhog Day was the fantastically witty 1993 movie whose hero - a cynical TV weatherman - is stuck in small-town America because he has been caught up in a repeating time-loop - if time-loops are a thing and can be repeated.
To this funny and unexpectedly thought-provoking plot, which manages to reveal that we are all to some extent trapped by our character flaws and foibles, composer/lyricist Tim Minchin has written a score every bit as good as the one he created for the musical Matilda.
Also crucial is the casting of American Andy Karl who, as Phil the weatherman, delivers one of the most commanding musical comedy performances I have seen. In fact, Karl is so good that not for a second do you miss Bill Murray who played Phil in the movie.
Tall, dark and with the kind of conventional good looks that could grace a knitwear catalogue, not a nanosecond of Karl's performance goes by without him extracting every scintilla of comedy and drama made available to him by Danny Rubin's well crafted script. Equally witty are Minchin's songs, the first of which sees Phil bemoan small-town America - a kind of civic version of Randy Newman's Short People.
So smooth you could ski down him, Phil is also deeply shallow and a fantastically selfish, nasty piece of work. His first instinct is to get out of the town he has been sent to because he thinks he's too good for it. You can't blame him.
He's there to report on a "moronic" tradition that sees a large rodent deified by the townspeople for its weather-prediction skills. When he realises he's trapped there and that his every action has no consequence, his second instinct is to have sex with all the women, including his producer Rita (Carlyss Peer), steal money and crash cars until the futility of it all leads him to a series of successful suicides. But even death ends up with him waking in the same chintzy B&B, on the same repeating morning.
The stage-craft with which this is achieved is so brilliantly executed I burst into spontaneous applause. One moment, Karl's Phil has topped himself at one end of the stage, the next he is rising out of bed for more self-harm at the other end. There's more darkness in the form of some beautifully observed songs that bring real depth to bit-part characters. If there's a minus to be found, maybe it's that Warchus stirs the emotions more than moves them. But then the same could have been said of the movie. There's no doubt about it. I could sit through this show again, and again and again.