Och hello there… Sir Sidney McSprocket here! 

Polly, my rather inquisitive parrot, has flown into the Victory Vault.  It’s my latest invention you know, a totally tremendous time machine that can take us to explore incredible inventions. 

I’d just finished my cuppa tee and set the parameters to explore inventions from the dark years of the 1940s when we were at war against Germany, Japan and their allies.  And now that silly old bird’s gone back in time without me. Come on, we better go and find her!

Looks like we’ve landed in some kind of ginormous factory with massive concrete structures.  Luckily I’ve brought my Chronophone with me. Another of my amazing inventions. Let’s see what can tell us.

Scanning Location:

• London… River Thames.
• Date – April 1944. Two months before D-Day.
• Invention detected – Construction of Caissons for the Mulberry Harbours.

Caissons

Now, are you thinking… what in the world is a caisson?!

Well, caissons were the backbone for the harbours that protected our troops when they landed on the Normandy beaches in France for the D-Day landings.

These caissons were all about getting boots on beaches. The minute our boys reach landed, engineers were right behind them, towing this lot over to France to get a full size harbour into place. It was a top secret mission – codename Mulberry.

The caissons were massive chambers, made of steel and concrete. When put together, they created strong harbour walls to protect our supply ships whilst they unload right on the beaches to keep our troops fed, armed and ready. 

How were they built?

Lot’s workers in factories across the UK built steel frames around which they poured concrete. Watch out for those sparks! 

Each caisson weighed between 1,600 and 6,000 tons, and used around 31,000 tons of steel. It’s a monstrous task, but there are 45,000 workers across the country chipping in – builders, welders, even folks who’ve never held a hammer before. 

The caissons were towed across the Channel, along with 6 miles of flexible steel roadways, and filled with water to keep them anchored on the seabed. The whole thing was like a giant puzzle, and there was only days to assemble them once in place. The workers didn’t know when or where they were going until the top brass told them. Got to keep it a surprise for the enemy, right?

Every piece has been tested to work out the kinks. Luckily there’s men like Sir Harold Werner solving problems as fast as they pop up. Bit gruff, that one, but a genius when it comes to engineering. 

Mulberry Harbours

The Mulberry Harbours were operational within 12 days of the D-Day landings. Whilst Mulberry A off Omaha Beach was destroyed in a storm a few days after it was built, Mulberry B off Gold Beach was used to land over 2.5 million troops, 500,000 vehicles and 4 million tonnes of supplies in the 10 months after D-Day.

You can still see some of the caissons at Thorpe Bay near Southend-on-Sea, at Portland Harbour in Dorset and at low tide at Pagham Harbour in West Sussex. If you’re in France, remains of the Mulberry harbour are still visible at Arromanches.

It’s amazing to think that with those caissons, the Mulberry Harbours were built so quickly to support the troops in France – who knows, without them things could have gone very differently…

Precast and prefabricated concrete structures are a big part of modern construction.  Not only do they help quality control and speed of construction, they offer flexibility in shape, width and weight, which can mean more dynamic structures. At 3.4km the Colne Valley Viaduct is the UK’s longest railway bridge and is made from 1,000 uniquely shaped precast deck segments, whilst the 16km Chiltern Tunnel is lined with 16,044 precast rings, each comprising 7 different segments – that’s a massive 112,000 segments.

Quite extraordinary wouldn’t you say? 

Oh no… Would you credit it? Polly’s flown into the Victory Vault again.  I better follow her… but maybe after a wee cuppa tee!  Tatty bye for now!

Build Your Own Harbour Wall

Use simple materials to build your own protective harbour wall, just like the Mulberry Harbours that helped Allied troops land safely in Normandy. Discover how prefabrication and teamwork played a huge part in one of the biggest engineering challenges of the war. Will your harbour keep the waves at bay? Get started here.

SIR SIDNEY MCSPROCKET AND THE VICTORY VAULT. Created with support from The Royal Commission for the Exhibition of 1851.