In time-honoured Open Air tradition, the stage management voice-over summoned the actors from the stage and explained that the Met Office had confirmed that the downpour would continue indefinitely; that paying customers would be supplied with tickets for a later performance; and that the reception for guests and the production team would go ahead anway in the marquee.
The show itself ended in Titania's bower as Hermia asked Lysander to do his best and pluck that crawling serpent from her breast. The bower was extraordinary: a long grassy knoll studded with colourful wild flowers and fairy lights that was the lowered nearside of one of the two large caravans on Jon Bausor's gypsy encampment setting.
As in this season's parallel production of Ragtime, the park has become an industrial urban melting pot where, in the case of the Dream, the spiritual, magical inner life of the fairy kingdom has been submerged in concrete, road works and the coming shopping mall.
It's a Jez Butterworth vision of the Dream and it seemed to be working brilliantly until we were so rudely cut off before the rehearsal scene - the mechanicals are the local construction workers, natch - and Bottom's acquisition of a donkey head. Helena and Hermia are a pair of gruesome chavs, Lysander and Demetrius street-fighting rivals in a gangland ruled by a thuggish Theseus and his battered new wife Hippolyta.
Soaked and sorely tested as we were, a large section of the audience, led by my immediate neighbours, the Haymarket Theatre producer Arnold Crook and the irrepressible Christopher Biggins, leapt to their feet in appreciation of the actors' efforts, Crook muttering to me as he did so that there must be easier ways for me to earn a living. The actors clapped them back. We'd all been through this thing together.
It had rained all day, and the forecast had never changed from being continuously dismal, so I was surprised in the first place that the theatre hadn't cancelled at lunchtime to give everyone a decent chance to re-group. But that's not how they do things in the park. I remember Ian Talbot, Timothy Sheader's predecessor as artistic director, telling me that, in the worst summer in living memory, they had lost only seven performances to the rain. They really do believe the show will go on, come hell or high water.
Well, hell and high water duly arrived yesterday. The season's casting director, Pippa Ailion, tripped in a puddle and fell flat on her face within 50 yards of the theatre's entrance (she was, remarkably, completely unharmed). Ushers distributed free noggins of ginger beer and plastic ponchos, or cagoules.
It was last orders on the Titanic, but Biggins and co continued with their undercover picnic notwithstanding, blithely helping themselves to best cuts of serrano pork and luxury salads washed down with red wine; at least champagne and Pimms had been eschewed in the cold.
I thought I was well wrapped up in four layers, including two weather-proof jackets, but I was still soaked to the skin when I got home. Mind you, my inexpert application of the plastic poncho hadn't helped. I think I'd put my head through one of the arm-holes. Or possibly put the poncho on the wet seat and the plastic seat-cover on my head. Either way, I betrayed, said Michael Billington, a woefully clumsy and uncoordinated condom technique.
I can only recall two previous press night wash-outs in the park: at Judi Dench's award-winning revival of The Boys from Syracuse for Ian Talbot and, before that, a Two Gentlemen of Verona in the David Conville era. Bernard Bresslaw was playing Launce in the latter and, when the actors were called off in a monsoon, he simply picked up his dog and said loudly, as though it were funny, "Rain stopped play."
At least I was home in time to see the last half hour of the Ukraine's thrilling victory over Sweden in the European soccer championship. I don't see England - whose scrappy draw against France was the warm-up torture for the park - beating either of those two teams in their group, so I confidently predict an early bath for our mediocre players.
And an early bath is what I enjoyed to the full last night, after I'd dried off and re-fuelled with a glass of wine, a mug of tea and a shed load of soluble aspirin. I dread to think how the actors have survived these past few horrible days, but at least no-one fell off the stage or pulled a muscle, as far as I could see. Hippolyta had a bruised face and a bandaged ankle, but that was because her nuptials with Theseus were fraught with physical violence on the camp site. I look forward to catching a dry run sometime soon.