Jay Merrick: Home of Shakespeare deserves architecture with a sense of drama

The Royal Shakespeare Theatre's transformation by Rab Bennetts has turned a famously stolid architectural mongrel into a re-branded 21st-century visitor experience that is, by turns, engrossing, neutral and strange.

Those equipped with decent binoculars, and standing on high ground in Warwickshire, Oxfordshire, Gloucestershire and Worcestershire can ogle its pièce de résistance, a tapering 36m-high brick exclamation mark of a tower whose design is puzzling, if not starkly questionable.

The architect, a charming fellow who fizzes around like a sherbert fountain, has skilfully delivered a series of big, functionally successful interventions. First and foremost, his practice Bennetts Associates, working with engineers Buro Happold and Charcoalblue theatre consultants, have created a superb and technically advanced drum-form auditorium with a deep thrust stage, and 1,040 seats in three tiers – none more than 15m from the front edge of the forestage.

Through the years, thousands have "suffered" from Shakespeare after sitting in the gods of the old fan-shaped auditorium, 27m from the proscenium.

When Anthony Quayle, an early director of the Shakespeare Memorial Theatre, asked the legendary Tyrone Guthrie to perform there, Guthrie replied: "I'll come if you bulldoze the proscenium stage into the river."

Bennetts has also opened up the building's river frontage gracefully and effectively with a riverside promenade that runs past the knobbly 1932 Art Deco facade designed by Elisabeth Scott, and skirts the flank of the Swan Theatre. The prom then segues into a path that leads to Holy Trinity Church, where Shakespeare was baptised and buried.

The key decision – to thrust, or not to thrust – only came at a late stage in the design development. Another late decision concerned spending £2m to dig a 7m deep thrust basement into the Avon's flood-plain – an unquestionably tricky, if not risky piece of engineering. But artistic director Michael Boyd now has the "tension and compression, and the full human presence" he craves.

The new architecture of the building has brought great advances to its functional, educational and pleasurable possibilities. And interesting portions of the original fabric have been saved from demolition, or very visibly re-used elsewhere; the floor of the original stage, for example, and the original Art Deco ticket office, which now rises hilariously on steel columns like a Wurlitzer organ to let people pass more easily into the canyon-like space between the foyer and the curving brick shoulder of the auditorium.

Nevertheless, the architectural props and make-up that clothe these changes are not always comfortably deployed. The glazed elements of the Southern Lane facade, and the three-storey glass box that links the new tower with the 1932 building, seem almost corporate; and inside the colonnade that connects the foyer and the Victorian segment, there is a sense of miss-matched parts.

As for the tower, it is a superb example of structural brick-laying, but its overwrought architectural details undermine its monumental heft, which has been fatally unzipped by the finnicky slit-glazing that skitters up its corners. Is this a modernist or a "contextual" tower? Alas, it is neither.