A total of fourteen 30m steel columns will be placed on piles already laid in Portsmouth harbour, in order to create the nautical equivalent of runway lights for the new Queen Elizabeth Class aircraft carriers that will dock there.
Work is near completion, with the piling already in place, and the 14 steel columns taking their positions on top before the lights are installed.
The first QE Class carrier is due to sail into Portsmouth in spring 2017, and the lighting towers will provide a visible indication of the route the vessel needs to line up with from some distance out.
Although other navigational systems will also help with this, the lights – which will be powered by solar panels and batteries – should remain operational even if other electronics are down.
Some discussion forum users have also suggested that the lights will help navigate the vessels as the steering position is off-centre, with one side of each carrier taken up by its runway.
A 350-tonne crane barge is being used to lift each 22-tonne steel column into place on its piling, with strict speed restrictions in place for other vessels passing close by.
Ships sailing past the barge are limited to six knots at most, and should still steer to allow it a wide berth; vessels that cannot slow down enough have been warned that they may face delays in being allowed into Portsmouth.
The work is also potentially subject to further delays if heavy weather sets in, as the barge will be affected by any large swells and waves.
Philip Wise, principal project manager for the Defence Infrastructure Organisation, said: “The navigation lights are essential to ensure the safe passage of the carriers into the naval base at Portsmouth.
“The work to install them represents a significant step forward in our preparations for the arrival of the two new ships, which will be the largest ever constructed for the Royal Navy.”