A layer of glass on the new walkway above Tower Bridge shattered when a sightseer dropped a beer bottle.
The stunning walkway allows visitors to look down from 40 metres as cars travel over the iconic bridge below.
But its "sacrificial layer" smashed when the glass bottle was dropped on Friday night.
The bridge remained open to the public and officials said no one was at risk.
Tower Bridge head Chris Earlie suggested new rules banning glass bottles on the walkway could be introduced after the incident.
<blockquote class="twitter-tweet" lang="en">Was in tower bridge walkway today, someone dropped a beer bottle; this happened <a rel="nofollow" target="_blank" href="https://www.awin1.com/awclick.php?mid=9&id=222025&p=http://t.co/fYFju69XBS" class="body-link" data-vars-item-name="BL-140451-http://t.co/fYFju69XBS" data-vars-event-id="c23">pic.twitter.com/fYFju69XBS</a>— Peter Gordon (@the1gordo) <a rel="nofollow" target="_blank" href="https://twitter.com/the1gordo/status/535931774774550528" class="body-link" data-vars-item-name="BL-140451-https://twitter.com/the1gordo/status/535931774774550528" data-vars-event-id="c23">November 21, 2014</a>
He told ITV: "We are gutted it's happened in the first couple of weeks when it's been open to the public but it's completely safe.
"We should have said no glass on the glass section of the floor. It was a bit shortsighted of us."
Tower Bridge glass walkway
Mr Earlie added: "The floor has five layers of glass with this sacrificial layer on top - it's there so we can replace it if it gets scratched.
"We are still open to the public and if we had any concerns we would have closed."
The walkway is 11m long, 1.8m wide, and made up of six panels, which are 68mm thick and each weigh approximately 530kg
