Russian constructivism at the Royal Academy

The courtyard of the Royal Academy is currently the setting for this steel tower, a striking twin spiral supported on zigzag bracing, but somewhat overwhelmed by the architecture surrounding it. It is in fact just a scale model of the tower designed in 1920 by Russian architect and engineer Vladimir Tatlin, just three years after the October Revolution and before the USSR was established. Designed as a monument to the Third International, only a model was built at the time, and now just Tatlin's drawings survive. If it had been built, it would be 400 metres high, higher than the Eiffel Tower in Paris.

It's widely held to be a masterpiece of Constructivism, the avant garde movement linked with the early years of the communist state - before reaction and repression set in. Conceived at a time that coincides with the Edwardian period in England, it's quite difficult to understand such an abrupt change, from the amazingly modern and forward-looking futuristic designs adopted by the budding socialist state, to the suppression of artistic expression that followed on all too soon.

Tatlin's masterpiece would have towered high above St Petersburg, but it was never built because of political uncertainty, perhaps because it was physically impossible, and because it would have been extraordinarily expensive. None the less it remains legendary both as an early expression of modernism, and as some kind of socialist icon.

The scale model at the RA was designed by architect Jeremy Dixon, who made a slightly smaller wooden version for an exhibition at the Hayward in 1971. This time around he has the benefit of computer aided modelling, not available in the 1970s, but because it's based upon drawings and photographs of the original model, none of which are the same, it's an interpretation rather than an exact scale copy. That circular base has nothing to do with Tatlin's design and rather spoils the effect of the dynamic form rising out of the ground, dissipating the vertical thrusting energy by introducing that broad wedding-cake base. No doubt that keeps it nice and stable, but it would have been better without it, better still if the whole thing was twice as big and really dominated the RA courtyard.