Joel Horwood’s new play, based on the characters by Arthur Conan Doyle, runs until 6 June

“The game’s afoot,” says Joshua James as Sherlock Holmes, the air so cold that the breath from his mouth hangs in front of his face. The opening night of the open air season at Regent’s Park has to be the chilliest on record – but the production featuring the Conan Doyle’s immortal detective has an almost feverish excitement to balance the temperature.
It’s all beautifully done. Joel Horwood has written a script, very loosely based on The Sign of Four, which features all the Holmesian elements you could wish for: lost treasure, a blood oath, a curse, conspiracy, skullduggery in high places, poison darts, a circus, and even a hot air balloon.
Into the traditional elements he has added a fair wallop of anti-Empire social commentary – “that treasure isn’t free wealth, it’s stolen history” – and psychological insight into the relationship between the lonely, obsessive Holmes and his fiction-writing sidekick Dr Watson (embodied with warmth and charisma and an excellent check suit by Jyuddah Jaymes).
The constant clarification of theme is over-emphatic, but the production is magnificently brought to life and quite literally framed by Grace Smart’s design which sets a broken gilded proscenium arch across a revolving stage, surrounded in the encroaching darkness beyond by odd bits of Victorian furniture and the rustling foliage of the Regent’s Park trees.
Figures lurk in those shadows and towards the close, as the night draws in and Ryan Day’s lighting design casts stark shadows, the blackness around the brightness of the playing area, full of bustle and life in Charlotte Broom’s busy movement direction, neatly supports the play’s central thesis about the great show of life being just tricks and illusion, disguising the effort needed to maintain the lie of power.
The design is indeed rather more subtle than some of the writing which has the obviousness of a hammer blow, and a plot that twists and turns bewilderingly before ending up where Holmes enthusiasts might always have guessed it would land. The entire venture, sustained by Sean Holmes’ energetic direction, is also overlong, though I admit it will probably seem shorter on a warmer night.
There are, however, scenes that truly entrance: a tube journey on the newly built underground that runs to nearby 221B Baker Street where the cast jolt and twist as the train runs over imaginary points; a boat chase down the Thames; the rich reds of a Victorian circus with fire-eaters and sword swallowers; fantastical journeys through Holmes’ mind as it whirrs through problems, bringing characters into play and making them reenact their actions.
Its essential strength springs from the two central performances. James, in shimmering blue, is a terrific Holmes, all nervous energy and twitchy thought, his rationality constantly battling Watson’s emotional responses. His comic timing is superb. There’s a moment where he barks “Don’t listen to him, he’s mad” where the crazed emphasis makes a simple line brilliantly funny.
But he’s matched by Jaymes’ gentler Watson, not the buffoon of many portrayals, but a clever man battling his own demons. Among a hard-working cast, many of them doubling frantically, Nadi Kemp-Sayfi’s self-possessed Mary, Patrick Warner as a drawling Mycroft, and Christopher Akrill in multiple tiny roles, stand out.