Is a £46m glass tiara the right way to remember the UK’s late queen? The Elizabeth II memorial selection committee certainly think so, in their choice of a glitzy glass bridge designed by Norman Foster for her permanent memorial in St James’s Park, announced on Tuesday.

As architects go, the 90-year-old Foster is perhaps the closest we have to a national treasure, so he might seem like a fitting choice – an establishment figure and safe pair of hands, who knew the queen personally. It could be an apt final project for the architect lord, although he shows no signs of slowing down.

His personal connection might have clinched the deal. Lord Foster of Thames Bank, who quit his seat in the House of Lords in 2010 in order to retain his non-dom tax status, says he met the queen on both formal and informal occasions, and it was this dual acquaintance that informed his design.

“She was wonderfully formal when the occasion demanded,” he recalls, “and warmly informal when she engaged with people and individuals.” His project attempts to “combine the formal and the informal”, riffing off a similar duality found in the landscape design of St James’s Park, laid out by John Nash in the 1820s.

In reaching for a suitably regal metaphor to embody the late monarch, Foster landed on her wedding tiara. He has accordingly conjured an ethereal vision of a bridge with a cast glass balustrade, shimmering above the lake. This translucent glass crossing, he says, will be “symbolic of Her Majesty as a unifying force, bringing together nations, countries, the Commonwealth, charities and the armed forces”.

So far, the images give off the vibes of a temporary Swarovski-sponsored installation, and it’s hard to imagine how the Royal Parks’ maintenance team will keep it looking quite so sparkly. The vision recalls Foster’s “blade of light” idea for the Millennium Bridge, which ended up being a good deal more chunky (and wobbly) than the dashing sketch promised.

Foster might have done well to take a closer look at the history of the tiara in question. It was originally designed in 1919 for Queen Mary, Elizabeth’s grandmother, a great lover of jewels, who had the headpiece made in the fashionable Russian kokoshnik style, using diamonds from an old necklace gifted to her by her mother-in-law, Queen Victoria. It was a model of recycling, which has been passed down the generations ever since – used by the Queen Mother, Elizabeth, Princess Anne, and most recently Princess Beatrice.

Not so Foster’s bridge. His project, which also includes a series of gardens, will see a perfectly good crossing needlessly destroyed. The existing Blue Bridge was built in 1957, to the designs of the Ministry of Works’ youngest ever chief architect, Eric Bedford, who went on to design the startlingly futuristic Post Office Tower (now BT Tower) in Fitzrovia. As it happens, Bedford also played a key role in Queen Elizabeth II’s coronation, designing a series of interlocking steel arches on the Mall, topped with lions and adorned with metalwork crowns and fan motifs, that were illuminated by night.

In our age of rapid global heating, when the carbon emissions of construction are closely counted by the kilo and architects strive to reuse as much existing fabric as possible, this wasteful act of demolition seems like a strange way to memorialise anyone. In selecting blocks of solid cast glass for his new bridge, Foster has chosen one of the most carbon-intensive materials available, given the furnaces must be heated to over 1,000C. Memorialising more than just the queen, this costly tiara will be an apt bookend to an age of excessive consumption.