Entry Requirements

Last night I joined the Royal Navy.
Excellent I thought, making something of my life at last.
Entry requirement was to fit through a tunnel, hexagenol in cross section.
As I was not of that shape I thought I might have difficulty.
It was a scary looking procedure and the fear was one of getting permanently stuck if it all went wrong.
I went for it however and duly found that as I pressed through, the navy blue coloured sides seem to accomodate my shape.
That was a relief and I accordingly found myself in the Royal Navy.
Rule Brittania.