Tower Bridge

There is an urban myth that the guy who bought London Bridge back in 1968 thought that he was really getting the distinctive Victorian mock-Gothic bridge that spans the Thames just by the Tower of London. Sadly, it is just a myth. Ever since the version that had all the houses and chapels (and the heads of executed traitors on spikes) on it, London Bridge has been a bit aesthetically boring.
Tower Bridge, built between 1886 and 1894, has also had its fair share of critics - who hated the "mockness" of it.
In the late Victorian period, it was realised that London needed a new bridge to the east of the City. There was a foot tunnel just to the east, but this wasn't sufficient for the needs of the growing dock district.
A competition was held for architects to submit designs - the only real stipulation being that the structure had to admit tall masted vessels to pass through to the Pool of London (the area up river). Very tall bridges were proposed, and swing ones, but eventually one that opened up in the middle was chosen. This caused some controversy, as the designer just happened to be one of the competition judges - Sir Horace Jones. He was chief architect for the City of London.
Sadly, he died before seeing his bridge completed. The bridge was officially opened on 30th June, 1894, by the then Prince of Wales (the future Edward VII).

It is a combined suspension and bascule bridge - the suspensions being the spans on the landward sides. Two steam engines powered the opening mechanisms, with a third being added during the Second World War as a back-up in case the bridge was targeted in a bombing raid. The bridge now hosts an exhibition, where you can see these. Recently, the exhibition added the further attraction of a glass floored section on the high walkways. Unfortunately, within a few days of opening, someone dropped a beer bottle and the supposedly reinforced glass cracked - so I advise caution should you choose to cross...

The openings and closings had to be covered by a complex set of visual and aural signals - both for the traffic on the road and for the vessels that were to pass through. Remember that for many years London suffered from what were known as "pea-soupers" - dense fogs which were a combination of meteorological and pollution effects. These days, if you want the bridge raised, you have to give 24 hours notice.
The central sections only rise as far as is needed for the particular vessel to pass through. If you happen to be the reigning monarch, however, the sections will rise to their fullest extent - no matter what size of craft they are in. The bridge would open to is fullest extent if Her Majesty were to go through in a pedalo, in other words.
The river traffic gets priority at all times, irrespective of road users. In 1997, US President Bill Clinton had his motorcade split in half when the bridge opened. Naturally, the chaps with the stony expressions, regulation dark glasses, and the little wires in their ears were not amused.

The bridge raises at 3.30pm on Sunday, 6th June 2015, to admit a tall masted sailing ship. This was exactly on schedule.

At least Clinton's driver didn't have to do what bus driver Albert Gunter had to do, back in 1952. His double-decker found itself on the bridge as it was opening. He accelerated and the bus leapt a three foot gap. Might not sound like much, but double-deckers are really not supposed to do that sort of thing. He was awarded a whole £10 pounds for his quick thinking.
On a couple of occasions pilots have flown through the gap between the road level and the high walkways without permission. One RAF pilot who did this in a Hawker Hunter was thrown out of the force, denied the opportunity to represent himself at his court martial. Another pilot, of a light aircraft, did the same thing in 1973, but he then flew up to the Lake District where he deliberately crashed and killed himself.
Originally, the metal work on the bridge was a greenish colour (it is now light blue). Back in 1977, for the Queen's Silver Jubilee, it was painted red, white and blue.
The southern approach to the bridge, in Southwark, was Horsleydown Lane. This was widened and is now called Tower Bridge Approach. The road is a major one - part of London's Inner Ring Road - so any prolonged closure causes considerable disruption and congestion. In 2003, a campaigner from Justice 4 Fathers, dressed as Spider-Man, climbed onto the walkway, and the bridge had to be closed for a whole 5 days.