Sir John Hawkshaw had designed the roof when Charing Cross opened in 1864. It was a single-span trussed arch with wrought-iron tie rods - a contained arch, with bowstring principals. The span was 164 feet wide and 510 feet long, one of the larger pieces of Victorian engineering in central London. Single-span roofs of this kind were a Victorian fascination: they covered station platforms without intermediate columns, leaving the working area underneath uncluttered. London had several. Cannon Street had one of the same type. So did St Pancras, though to a different design. The drawback - which became horribly clear at Charing Cross - was that the whole structure depended on the integrity of relatively few critical components. A failure in one tie rod could compromise an entire span. There was no fall-back mechanism, no secondary support to catch the load if the primary system failed.

On 5 December 1905 a gang of workmen were on the roof carrying out a long-term maintenance project - repairing, glazing, and painting one of the end bays at the southern (river) end of the structure. The roof was, by the standards of routine maintenance, heavily loaded with scaffolding and materials. When the tie rod sheared just before 3:45 p.m., the loud noise alerted people below. Quick thinking by the South Eastern and Chatham Railway staff in those twelve minutes prevented disaster. They evacuated passengers from platforms 3 to 6, where four passenger trains stood. They held back trains approaching the station. By the time the roof actually collapsed at 3:57 p.m., the platforms were largely clear. The glass wind-screen at the river end of the station came down with the roof. The girders and debris fell across the tracks and the four trains - but most of the people who would have been killed had already moved.

Six people lost their lives. Two were workmen on the roof itself, men who had been doing the maintenance and had no chance when the tie rod failed beneath them. One was an employee of W.H. Smith, working at a bookstall on the concourse - one of the small commercial fixtures that lined every major Victorian station, selling newspapers and railway novels to departing passengers. The other three deaths happened in a building that was not even part of the station. When the western side wall of the roof came down, it crashed through the wall and roof of the neighbouring Royal Avenue Theatre on Northumberland Avenue. The theatre - which later reopened as the Playhouse Theatre, the one still standing today - was being reconstructed at the time. Three workmen on the theatre site, doing entirely unrelated work, were killed when the station's western wall fell on them. Eight more workmen were seriously injured and taken to hospital; nineteen others suffered minor injuries. Compared to what could have happened on a busy weekday afternoon at one of London's busiest stations, the casualty list was remarkably small. But six families lost someone, and three of them were people who had every reason to assume that their workplace was nothing to do with a railway.

The closure of Charing Cross while the wreckage was cleared and the structure repaired had an unexpected consequence. The Charing Cross, Euston and Hampstead Railway - the underground line that would eventually become part of the London Underground's Northern line - was already planning to build a Charing Cross deep-level tube station beneath the mainline forecourt. Their original plan was to excavate upward from platform level, a delicate procedure that would not have disturbed mainline operations. With the station closed anyway, they were able to do the opposite: dig a large excavation downward from the forecourt - work that would not normally have been permitted while trains were running. The Charing Cross Underground station that opened on 22 June 1907 was therefore partly built in the gap left by the collapse. Disaster, in this case, made an unrelated project easier.

The Board of Trade inquiry attributed the immediate cause of the failure to a faulty weld in a tie rod - a single defective component. But the experts who gave evidence raised broader doubts about the design itself, including the safety factor against failure. If one undetected flaw could bring down 70 feet of arch and a section of side wall, then the engineering margin had been inadequate. The South Eastern and Chatham Railway initially believed the roof had at least forty more years of life. After the inquiry, they decided not to repair it at all. They replaced the entire arch. A travelling timber gantry had to be constructed to take down the remainder of the original roof safely. What went up in its place was utilitarian - a post-and-girder structure supporting a ridge-and-furrow roof. Less elegant, less dramatic, but with built-in redundancy: if one girder failed, the others would carry the load. The station partially reopened on 19 March 1906, less than four months after the collapse. Cannon Street station's similar single-span roof was eventually taken down in 1958 - a delayed second consequence of what happened at Charing Cross. The curve of Hawkshaw's original arch can still be traced today in the brickwork of the side walls of the station, a ghost outline of an engineering decision that needed twelve minutes of warning to keep from killing many more people than it actually did.