Partly because this theatre above all theatres channels an unbroken atmosphere of unbridled jollity (and not just at Christmas) between stage and stalls. And partly because I needed to nab a few friends and say hello.
There is, on nights like these, at least, a real sense of historic continuity round Gerry Raffles Square from the mercurial presence of Joan Littlewood in the 1950s and 1960s right through to the high-spirited generosity of Kerry Michael in the present day.
And the audience is a demonstration of that. It's mostly local -- more local than in Joan's day, that's for sure -- and wonderfully raucous, but there's always room for dignitaries like Neil and Glenys Kinnock, who were taking care of some tiny tots (and having pizza with them before the show).
Littlewood's own era was represented by playwright Peter Rankin, stage manager and jazz muso John Wallbank, and lighting designer Mark Pritchard. Then there was Littlewood's successor, Philip Hedley, along with Toni Palmer and Peter Straker. And with lights twinkling and red wine flowing, it certainly seemed like Christmas.
It's always something of a mystery to me how shows actually open on time. It's rare to have delays, but they are not uncommon in musicals. Nor is it uncommon to have a critics' call back once a complicated musical show has been running for a few months. This certainly happened with Martin Guerre, which became much better, but no bigger a success.
So it will be intriguing to see how next week's new Press night for Love Never Dies fares a) with those who liked it very much first time round (myself, the Independent and the Daily Telegraph included) and b) with those who disliked it intensely.
The only point of the invitation from a management's perspective is the possibility of recantation as a result of months of fiddling by the first director, Jack O'Brien, and a more recent make-over by his replacement -- allegedly for the Australian and Canadian productions -- Bill Kenwright.
Why does this matter? Because only with more investment and confidence can those second productions go ahead, let alone try and unpick the damage done by the gleeful blogging about a show re-named "Paint Never Dries."
But the shilly-shallying surrounding this production -- which seemed absolutely five-star fabulous to me last March -- seems a somewhat weak-kneed response to the gossips and ne'er-do-wells of the blogosphere. And then of course, Broadway hopes were dismantled by a savage, uncharacteristically bitchy review by Ben Brantley in the New York Times.
So the producers booked this coming Monday in the Society of London Theatre diary as the new Press night. Then they changed it to Tuesday. Now it's gone back to Monday, with some critics going on Tuesday, and an embargo on reviews till Wednesday.
To add to the confusion, the President of the drama section of the Critics Circle, Mark Shenton, has already blogged a spectacular U-turn on the show and declared that Bill Kenwright's overhaul has saved the day.
It will be interesting to see what it is that Kenwright has done (apart from cut Madame Giry's first song, apparently, leaving poor Liz Robertson deeply hurt and upset; this would make a nonsense of the flash-back, ghostly retrospective framework of the whole show).
We shall see, but no one must doubt that all this fiddling about is about one thing, and one thing only: getting the show onto Broadway and stuffing the bad reviews down the dissenting critics' throats.
Personally, I feel sympathetic towards Lloyd Webber's intentions in this regard. His score is a beauty, every note as good as the first Phantom, if lacking a few obvious points of climactic theatricality.
And, after all, another critic, Paul Taylor, praised both the technical excellence of Jack O'Brien's production as "seamlessly fluent, sumptuous, sometimes subtle" and the "splendour of the orchestra which pours forth Lloyd Webber's dark-hued, yearning melodies as if its life depended on them." Let's see what gives.