As the UK prepares for its most significant solar eclipse in nearly three decades, a nationwide shortage of certified eclipse glasses has emerged, leaving many enthusiasts scrambling to find safe viewing equipment.

At a central London bakery, staff report selling around 100 pairs of eclipse glasses in a single morning, with customers queuing not for pastries but for the protective eyewear. One buyer, who arrived too late to order online, told BBC Radio 4's PM programme: "I Googled 'where can I get eclipse glasses but not through the post', because I realised I was too late."

The Royal Museums Greenwich, a recommended retailer by UK health officials, has also sold out, citing an "unprecedented volume" of orders. Online, most glasses meeting safety standards are either unavailable or cannot be delivered in time for Wednesday's event.

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Experts stress that looking directly at the Sun can cause lasting eye damage, even with brief exposure. The UK Health Security Agency (UKHSA) advises that proper glasses must carry the international safety standard ISO 12312-2 and be free of scratches or damage. They also recommend buying new glasses rather than reusing pairs from the 1999 eclipse.

With about 90% of the Sun expected to be obscured by the Moon, the event is drawing widespread attention. However, the scramble has also raised concerns about counterfeit products. UKEclipse, an initiative by UK astronomers, warns that major eclipses often attract "counterfeit and substandard" glasses and advises purchasing from specialist retailers.

The American Astronomical Society (AAS) suggests checking its list of manufacturers that have verified their glasses in a lab. They recommend testing glasses indoors and outdoors on a sunny day; if only very bright lights are visible, the glasses are likely safe. A quick glance at the Sun should reveal a "sharp-edged, round disk" that is "comfortably bright" against a dark background.

The Royal College of Ophthalmologists warns that even a small gap in the glasses can harm the eyes. "Crucially, the retina has no pain receptors, so people will not feel the damage as it happens," explains college president Mohamed Elalfy. The college reported about 70 cases of vision problems after the 1999 eclipse, with around 40% of those affected having looked at the Sun for less than a minute.

Regular sunglasses are not a safe alternative, as they can reduce glare and encourage longer, more damaging exposure. Binoculars, telescopes, and camera viewfinders should also be avoided, even with eclipse glasses on, due to their magnifying effect.

For those without glasses, experts recommend indirect viewing methods such as pinhole projectors made from card or cardboard boxes. Imo Bell, a planetarium astronomer at The Royal Observatory Greenwich, emphasized the importance of preparation: "We're not going to get one this good for a really long time. So, it's important not to miss it, and to be prepared."

Source: BBC News