How we learned to love the Lloyds building

Twenty-five years young, the Lloyd's building is still shockingly new. Yesterday it was announced that this hi-tech City of London tour-de-force, designed by the Richard Rogers Partnership, has been listed Grade I by heritage minister John Penrose. The youngest to be granted that special status, it joins company with a select band of postwar buildings including the Royal Festival Hall and Coventry Cathedral.

Lloyds is also the first Grade I-listed building designed specifically for change. While listing protects historic monuments from insensitive alteration, the whole point of this late 20th-century reworking of Joseph Paxton's Crystal Palace, crossed with a North Sea oil-rig, is the flexible space it offers, and the promise that, one day, it might be re-arranged as easily as if it had been assembled from Meccano.

The inside-out, or "bowellist", look of the 88-metre high concrete structure, with its external wall-climbing glass lifts, exposed pipework and plug-in, stainless steel clad lavatory pods, is graphic evidence of the way this breathtaking ensemble was clipped together like a giant kit of parts.

Naturally, Lloyds has never been to everyone's taste – too much like an oil-refinery thumped down next to Wren's City churches and Neo-Classical banks clad in Portland stone – and its provocative design is all the more remarkable given that it was commissioned by and for apparently conservative, pin-striped City types.

With its soaring central atrium, the radical, open-plan interior is nothing short of sensational. Even then, it abounds in surprises. High up in the building, a door opens to reveal a complete Robert Adam boardroom of the 1760s, representing most people's idea of what Grade I listed buildings look like. Attitudes to modern architecture have clearly changed.

The biggest change of all since then, however, has been among conservationists themselves: in the 1980s, they tended to see Lloyds as a modern monstrosity. Now they love it.