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Attached is a series of photos from a previous phase, detailing the work - from breaking out the old track through to the new track being in place.

The work on the lines uses rail fixings called Vipa base plates to hold in place the two rails that make up the railway track. The base plates also cut down on noise and vibration, so rail passengers get a smoother, quieter ride.

The underground system in Liverpool is unusual compared to conventional railway tracks. Most track systems consist of two rails held in place on sleepers by steel clips. The sleepers, which can be either wooden, steel or concrete, are packed into ballast.

However, the four mile long Liverpool underground system constructed in 1971 consists of a circular loop line in a single bore tunnel, bringing trains in from Chester and the Wirral, crossed at a slightly higher level by tunnels carrying the north/south Northern Line between Southport and Hunts Cross. The railway lines sit on base plates which are bolted onto a solid slab of concrete that takes the place of the sleepers and ballast. This system is used because of the limited clearance in the tunnels and the need to make sure that the track does not move out of alignment.

The work involves taking up the old track and using drills to break up the existing concrete base.

Once the debris has been removed, wooden shuttering is put in place to hold the concrete that will form the new base.

The concrete is poured and once set, holes are drilled in the new slab and the base plates are fixed in place before the new rails are positioned.

The final alignment of the track is done with lasers before the rails are secured in position.

Almost the last piece in the work jigsaw is to put back the third rail that carries the 750 volts of electricity needed to power the trains, before the stations are given a thorough clean ready for passengers to start using them again.