Just 48 hours before the conclusion of the Conservative leadership contest, Allan Cook, chairman of HS2, wrote to the government to confess that the costs of the project could rise from the current projection of £56 billion to as much as £86 billion. Given that Boris had already announced that he is to review the project, it was pretty much akin to a condemned prisoner writing a letter of confession.

The Prime Minister is not fond of doomsters and gloomsters who pooh-pooh things for the sake of it, and as we know is partial to the odd vanity project. More-over, he seems as fond of trains as he is of model buses. But he could do us all a favour by ditching the wretched HS2 and replacing it with a far cheaper and more practical alternative — a project which actually offers something to the communities which have been fighting the high speed link and which, while speeding up and improving rail links from London northwards, would also release billions of pounds for much needed improvements to public transport between and within northern cities.

That alternative is the little-known Great Central Railway. This ready-made high-speed line takes almost exactly the same route between London and the Midlands as HS2 would. It sits there, its viaducts and bridges unused, begging for trains. It did once have them — at one point it had the fastest expresses in the country. Opened in 1899, it was the last and the best--engineered of all the main lines in Britain. It was built with the vision of operating 125mph expresses, and used a ‘continental loading gauge’ — which means that, uniquely for British lines, the wider trains used in mainland Europe could be run along it.

The Great Central was one of the many casualties of the Beeching closures of the 1960s, yet it remains almost totally intact. A few agricultural buildings have been built across it, but otherwise its line remains clear — a recently-built housing estate in Brackley, Northamptonshire, respectfully leaves its course as an undeveloped green corridor, just in case. There is a question of what would happen at the London end — whether to share existing tracks to Paddington or Marylebone, or to tunnel to Euston. But for much of its length the Great Central could be reinstated with little earth-moving, tunnelling and without the need to demolish residential properties or foul sites of special scientific interest.

The reopening of the line has, indeed, already been mooted. Between 1996 and 2003 a private company, Central Railway, did extensive work on reinstating the line as a goods and passenger route. At the time when the project was dismissed by the Blair government in 2003, its cost was put at £8 billion — and that included upgrading and reopening sections all the way to Liverpool. The project then briefly resurfaced again in 2013, when Ed Miliband’s Labour looked at it as a cheaper alternative to HS2.

The Great Central fulfils all the main objectives of HS2 without the excruciating cost, the environmental objections and absurdities of the latter project. True, no train on the Great Central is going to reach 225mph — the projected speed for HS2. A maximum line speed of 140mph is more realistic. But then no one has ever explained why a compact country like Britain needs the fastest long-distance railway in the world, other than for the purpose of national willy-waving. International experience suggests that high-speed railways transform the market for travel between cities — knocking out airlines and creating a substantial new market for day-return travel — when they reduce journey times to below about two and a half hours.

Yet the cities which would be linked by HS2 — London, Birmingham, Manchester and Leeds — already are within this travel time. Small reductions in travel times have to be weighed against other factors. As HS2 trains would require advance booking and not be available to passengers who want to turn up and go, there is little point in shaving 20 minutes off your journey if you are then going to have to turn up at the station 20 minutes earlier to be sure of catching the train on which you are booked. HS2 would only really be justified if the new lines went on to Newcastle, Edinburgh and Glasgow, but it doesn’t.

Meanwhile, the disadvantage of running trains at 225mph is that they can’t stop very often. As a result, HS2 misses out the towns which are most in need of regeneration: Stoke-on-Trent, Coventry, Leicester. Derby and Nottingham would be served by a station between the two — requiring a long tram ride to the centre of either. In Birmingham, HS2 trains would terminate at a new station, Curzon Street, rather than New Street, where all the connections are to other towns in the West Midlands. As for East Midlands airport — that is the most ludicrous situation of all. Which other country would burrow a high-speed rail line under the runway of an international airport and not have a station there?

A reopened Great Central line, by contrast, would plug much more naturally into the existing rail network. Moreover, it would allow two new stations to be built at important locations — at Brackley, a growing part of Northamptonshire which has not had a rail service since the 1960s, and at the intersection with the old Oxford to Cambridge line, itself the subject of reinstatement proposals. The Oxford to Cambridge corridor has been proposed as a growth area for development in decades — why not put a high-speed rail station with connections north and south bang in the middle of it?

The main job of the Great Central line would be to create extra capacity between London and Rugby, to relieve pressure on the West Coast main line. North of that point, there are fewer capacity problems because the West Coast main line splits, one section going to Birmingham, the other towards Stafford. As for the billions saved by not building HS2 — just a fraction of the money could transform public transport in northern cities. The proposed three-line Merseytram, abandoned in 2005 after a disagreement between the Blair government and the Merseyside authority over who would underwrite the financial risk, was costed at £325 million, less than 1 per cent of HS2. The similarly abandoned Leeds supertram was similarly costed at £500 million.

In backing a new Transpennine line, Boris has signalled he understands where investment is most urgently required — between and within provincial cities. He can find the cash — without abandoning the need for an extra north-south inter-city line — by reviving a forgotten gem of Victorian engineering.