"It’s a different side to Sherlock Holmes — one I hadn’t expected,” I heard a member of the audience say during the interval — and that was before the ‘secret’ that is the twist in this generally pleasing two-hander.

The play originated in 1988 as a stage vehicle for Jeremy Brett and Edward Hardwicke when they were appearing in the hugely successful Granada Television Sherlock Holmes series. Written by one of the scriptwriters for that series, Jeremy Paul, it is essentially a 90-minute cuttings job from the Holmes Canon — a ‘best of’ with lots of quotations.

What it is not is a Sherlock Holmes story or thriller. Rather, it is an introduction to those who know not of Holmes (is there anyone on the planet?), a comforting reminder for much of the time of why those who do know love the Holmes-Watson relationship and, in its final quarter, an exploration of the bleaker side of the great Baker Street consulting detective.

Peter Egan (Holmes) has been touring this vehicle around the country for much of the year and the company has struck lucky in getting a late gig in the West End (admittedly for only eight weeks) after the premature closure of another play. For this outing, Egan is joined by Robert Daws as Watson, who plays this vital character well.

One day, the doctor as the comic bumbler portrayed by Nigel Bruce in the films with Basil Rathbone will finally be forgotten; and actors such as Nigel Stock, David Burke, Edward Hardwicke and this year’s cinematic sensation Jude Law have worked hard over the decades to achieve this aim. Daws’s name can justifiably be added to that list.

Peter Egan knows how to command a stage. His Holmes is laconic, shows a dry wit and hints — well before the ‘secret’ is revealed — at interesting psychological depths. He is eminently watchable, an older and wiser Sherlock but one capable of sudden explosion. The format of the play requires him to be ruminative, with little opportunity to play this iconic character at anything like the full throttle achieved on the stage in years past by such as John Wood and Keith Michell.

There is, it has to be said, a third, looming presence: that of Professor Moriarty. His part in Holmes’s life at all levels is covered at some length after the unnecessary interval — and maybe the ‘secret’ is a touch predictable.

My dear Watson, the tourists will simply flood in.

The play is at the Duchess Theatre until September 11. Box office: 0844 412 4659.

n Nick Utechin has been a member of The Sherlock Holmes Society of London since 1966 and edited its journal for 30 years. He also likes to point out that he’s related to Basil Rathbone.in.