ballast

The species has colonized new regions when transported on ships’ hulls or in ballast water that is drained in ports.

In each country where the mussels have taken over, the initial introduction also appeared to be from ships — on the hulls or from ballast water release.

The savings would be delivered through lower design speeds, ballasted track, UK rather than European standard cross-sections and building on the existing rail network.

Mr Williams said it was important the stones do not get depleted as the existing stones "came from all over the world and it was used as ballast" for the coal industry.

May makes the story her own, losing Simon’s penchant for shtick and leaning on her actors for emotional ballast.