BORIS Johnson has become the latest high-profile politician to express interest in the Scottish Government's aim to extend a high speed rail network north of the Border.

The engagement of the London Mayor follows a campaign by Scottish Transport Minister Keith Brown to sign up a "coalition of the eager" to support a cross-border route, which has so far been backed by 17 councils in the north of England.

In a letter dated June 19, Mr Johnson said his officials at Transport for London would be willing to meet counterparts at Transport Scotland to discuss the plans, adding that one of the mandates of the Mayor's office was to "modernise our transport network".

Mr Brown said he had been trying to build on the support of business groups, trade unions and lobby groups in Scotland as the arguments for extending a high speed rail network north of Birmingham were applicable to many towns and cities in the north of England.

"The benefits really start to take off the further north you come. We've been engaging with many of the other councils who perhaps, north of Birmingham and Manchester, feel they are in danger of losing out," he said.

"They see as well as we do the coming pressure on freight and passenger services beyond the mid-2020s if this is not to be addressed by high speed rail. I think what we've tried to get is a coalition of the eager, the people that want to see it come further north for the best reasons. We're not the only voice in this."