NOBODY can accuse Metrotidal of not thinking big. The consortium has been formed to promote a scheme that combines the long-proposed Lower Thames Crossing with a tidal barrage and tidal power scheme.

Into this package it also throws a quite new idea, a sub-Thames rail tunnel.

This would be the key element in a north-south link between the promised Crossrail, Canvey and the Medway towns.

The scale and cost are daunting, but there is nothing wrong with thinking big and bold. It is easy to be sceptical, but the idea deserves better than to be dismissed as pie in the sky.

After all, the technology involved - land reclamation, undersea tunnelling - is so tried and tested it can almost be described as traditional.

By sinking much of the work out of sight, Metrotidal banishes the spectre of pollution, both visual and effluent, and makes the scheme environmentally respectable.

Throw in the moneyspinning capacity of the Dartford bridge and tunnels, not to mention power generation, and you have a mix that may not be so unrealistic. Metrotidal has also grasped the fact that the need for a lower Thames tidal barrage is becoming increasingly urgent. So if it is inevitable, why not combine it with a crossing?

The implications for the south Essex economy if this scheme happened would be enormous. Strategically, it makes sense.

It could create an axis of prosperity between East Anglia and Kent. The cost, technology and possible disruption need to be thought through.

But the overwhelming ambitiousness of this scheme should not deter us from taking it seriously.