Tower Bridge is going to open its bascules.

...the bascules are the bit that the road sits on down below.

A sailing barge called Will wants to pass through the bridge,

and so the bridge must lift.

That's going to delight the tourists,

but it's going to delay thousands of drivers, cyclists, and pedestrians,

and cause tailbacks for miles.

And the team here

are going to let me push the button to do it.

But before we get to that point,

there's a lot of work to be done by a lot of different people.

- Sailing barge Will, Tower Bridge radio.

- "Tower Bridge radio, sailing barge Will, good morning."

- Yeah, good morning to you.

Just to let you know that we are standing by

for your 10:30 bridge lift.

- We work really closely with a number of agencies,

with the Port of London Authority, responsible for the river,

with Transport for London,

with the police as well, and also the local boroughs.

The bridge is sat between two boroughs of London,

half of it's in Tower Hamlets, and half of it's in Southwark,

so, in terms of transport network,

we need really close working relationships.

If we know that, for example, there's an ambulance on the way,

we'll hold off from starting the process.

- Tower Bridge is a tourist attraction these days.

That's why they've got the behind-the-scenes tours

and the glass floors up on the walkways,

but it's still a working bridge, and it can be opened,

must legally be opened,

to let river traffic through any hour of any day.

- There was this one time, back when Clinton and Blair were in power,

and I think their timings ran over slightly,

and the motorcade started to come back across the bridge,

from the south side to the north,

and got cut off by a bridge lift that was due to take place.

Now at that point, the bridge driver on duty received a call,

"there's a very important person in the car

"that's stuck on the south side of the bridge",

Bill Clinton, at the time.

The person in charge said, very bravely,

"No, we can't do that I'm afraid.

"The river traffic has rights over road traffic,

"but also, physics.

"There's a boat bearing down on us,

"if we don't raise the bridge, it'll strike the bridge."

So, they raised the bridge, it came through,

and they received a lovely letter from the White House

a couple of weeks later saying,

"Thank you for arranging the brilliant spectacle for us

"of Tower Bridge raising"!

- When Tower Bridge was built,

cargo was unloaded all around here, straight into warehouses on the riverbank,

so it was important that ships could get through the new bridge here.

River traffic comes first. Trade must not be interrupted.

That was laid down in law in 1885 when the bridge was commissioned, and,

even there's no cargo being unloaded around here these days,

that law hasn't changed.

Boats have a right to pass through here

and removing a legal right of way is very difficult.

There have been a couple of grumbles about it

in Parliament over the years, but as far as I can tell,

no one's ever seriously thought about changing it.

So, with 15 minutes to go,

the engineers are getting ready for the lift.

- We do have pre-checklists

to make sure that there's no obstructions in the bascules.

We check the oil levels. We check the electrics,

because we've got high voltage electricity coming in here.

So, when the bridge actually moves,

it's the initial torque that you've got to get,

once it actually starts moving,

it's quite straightforward and nice and easy.

We've got four packs on each corner of the bridge,

and one hydraulic pack has two hydraulic motors

with two hydraulic pumps.

Back in the day, up until the early '70s, it was steam operated.

What we actually use today

is very similar to what the Victorians actually put in,

and these days, it's just the electric hydraulics.

- If you've got a tall enough boat,

then you can call Tower Bridge 24 hours ahead,

ask for a bridge lift, and they will fit you in.

Even though you can't really get very far.

The next bridge is only about 900 metres down the river, and it doesn't move.

And never mind that lifting Tower Bridge causes tailbacks and

massively inconveniences a lot of people!

If your boat's tall enough,

then you've got a right to get the bridge lifted,

and about five minutes' time,

someone's going to use that right.

- Official numbers are six bridge drivers,

and so there's only six of us in the world that can actually do it.

It takes, on average, about two years to train up to be a bridge driver.

The main part of being a bridge driver

is not actually raising and lowering the bridge,

it's knowing what to do if it goes wrong.

If you've got the bridge up in the air, and it breaks down,

it's a matter of: you've got to be able to fix it as quick as possible,

so that you're not blocking up half of London.

[announcing] "Bridge driving control systems about to be switched on.

"Stand clear of moving structures, machinery, and controls."

- All right.

- Hi, Tom. - Hello!

- Come on in. - Thank you!

- Welcome to the northeast control cabin. - Thank you very much.

- As you know, we're about to do a bridge lift.

- Yep.

- It's going to be for the Sailing Barge Will,

which is just down the river, just down there.

- All right. - Time is now...

- 10:26. - Yeah.

- Four minutes. - So we're going to go straight into this.

- Let's do it. - No time to waste.

- I'm actually nervous.

- So the first thing I want you to do is start the power hydraulic pumps.

- Okay. - So, press that button.

That will now start the pumps.

"This is a public announcement.

"Bridge lifting operations are about to commence.

"Stand by bridge staff, stopping road traffic."

If you could just press the red traffic light?

- Traffic lights changing to red. [brakes squeal]

- That's it, let go.

So, now we can press them together, at this juncture.

- Done. - Now we'll press for the pedestrian gates.

- All right.

Closed? - Yep.

- Just got to wait for two casually sauntering tourists going across there.

- Yeah, this is why we start a little bit earlier.

- Are you ever tempted to just start it raising at this point?

- [laughs] No.

Press that now.

- All right, that's disengaging.

- Yep, so the indication will show... - That light's gone off.

I'm terrified I've pushed a wrong button already.

- No, no, you've done nothing wrong.

Next one is the nose bolts.

- Retract the nose bolts? - Yep, press that button.

- I feel like I should hold it down for longer,

but it's just a quick tap.

- It's just a quick tap.

- Bridge ready to move. - Yep.

- Grab hold of the joystick, pull it back slightly,

- Whoo! - Little bit more.

- All the way? All the way.

- That's it, all the way.

- Tell me... - You're now raisin' the bridge.

- Yep, tell me when to slow it down.

- It's going to be a matter of once we get to the angle,

you just let go of the joystick.

- Now, to me, from here, that looks like 45 already,

but we're only at 26.

- That's right. - It's deceiving.

- The way to see, at the corner of the bridge there,

you see that bit of iron with riveting? - Yeah.

- When that gets horizontal, that's actually 45 degrees.

- And here comes the barge.

That is much taller than it looked from a distance.

- It does.

- 39 degrees and 41.

- Right, so if you let go of it now,

and press the green river light... that's it.

- And Sailing Barge Will, is good to go.

- Yep. - It's a shame I'm wearing the mask,

because you can't see the grin on my face right now.

- It's a great feeling when you do it for the first time.

- Yeah.

Thank you so much!

- You have completed a bridge lift.

- That was much more nerve-racking,

than just pushing some buttons should have been.

There's so much riding on that.

I know it's all automated. I know that, at any point,

you could have pushed me out of the way and stepped in and that's fine,

but it's still nerve-racking when there are so many people waiting

and so much riding on that for, you know...London working.

- But even now, I've done hundreds of lifts,

and I still get a buzz out of it.

- Yeah!

Right, how do we get this back down?