In pictures: D-Day inventions

To keep advancing troops supplied, the US and British forces each built an improvised floating harbour, codenamed Mulberry.

The sections were towed across the Channel by tugs. The breakwater was built out of a series of huge hollow concrete blocks, some with anti-aircraft guns on top.

The pier heads rose and fell with the tide on adjustable legs, allowing stores to be unloaded at all times.

Unfortunately, the US Mulberry was destroyed by storms after only a few days.