The 3ft 3in (1m) square iconic panel, is one of two painted in gesso on hessian that were created by Macdonald Mackintosh for the Glasgow group's stand at the landmark 1902 International Exhibition of Modern Decorative Art in Turin.
This example, titled The White Rose and the Red Rose, and its companion, The Heart of the Rose, both featured in the stand's Rose Boudoir. They were offered here by an American who acquired them at Sotheby's New York in 1991 for $80,000 and $120,000 (then £53,675 and £80,512).
Again offered separately, each was estimated at £200,000-300,000 and initially when this example was offered, it looked as though Christie's estimate would not be far off.
But a masterful rostrum performance at the sale on April 30 from auctioneer Philippe Garner turned the tide.
Bidding opened at £140,000 and London dealer Michael Whiteway, acting for an unnamed institution, stepped up to the plate first. He dropped out at £360,000 to the American collector, who was bidding via the phone, and it looked as though the panel might sell at £380,000, but another phone, manned by Christie's Impressionist specialist Matthew Stephenson, decided to step in.
Over the space of several long minutes Mr Garner managed to inch these two phones, bidding in increments as low as £10,000 for much of the time, up to the final £1.5m, bringing down the hammer to a well-deserved round of applause.
With this price achieved, all eyes were on the second panel. Would there be another battle or, having lost the opportunity to secure both, would the underbidder let the successful buyer take the second relatively cheaply?
Things panned out rather differently. The successful purchaser seemed happy with one Glasgow school panel and did not even contest the second.
It was left to Michael Whiteway and the other phone to vie for The Heart of the Rose at a much more muted level, with Whiteway again unsuccessful, bowing out when his competitor bid £420,000.
The same phone was left with money to spare for the sculpture section, paying out some multi-estimate prices for Chiparus bronze and ivory dancers.
The £1.5m paid for The White Rose and Red Rose constitutes a new auction record for any Scottish work of art and is far more than for any previous work by the artist.
Nonetheless, the price compares favourably with the multi-million pound prices commanded by Macdonald Mackintosh's contemporaries Gustav Klimt and Egon Schiele, whose Secessionist attenuated figure studies were part of the same pan-European movement.
By Anne Crane