Former Concorde pilot Captain William “Jock” Lowe can remember exactly where he was when he had his Eureka moment, even though it was a quarter of a century ago.

It was 1988 and he was having dinner at a restaurant in Dubai with the UK’s then head of air traffic control. The dinner topic was one of Lowe’s greatest bugbears – capacity at Heathrow.

Lowe picked up a pen and started sketching out a few ideas on a napkin on how to expand Britain’s busiest airport within the land available.

Fast-forward 25 years and those ideas have been shortlisted by a commission investigating where to build the next runway in the south east of England.

Lowe is one of the directors behind Heathrow Hub, a private company that is proposing to take Heathrow’s existing northern runway, extend it to 6,000 metres and introduce a 600m safety zone so it can effectively be used as two separate take-off and landing strips.

Heathrow Hub’s inclusion on a shortlist of just three published last week by the Airports Commission caught many off guard. It was the surprise of the week.

The group’s idea will be taken forward for further investigation along with plans for a second runway at Gatwick and proposals by Heathrow Airport itself for a third runway to the north west of its current site, over the villages of Longford and Harmondsworth near West Drayton.

Lowe was stepping off a plane from Brazil on Tuesday morning when the commission’s chairman, Sir Howard Davies, unveiled his shortlist following weeks of speculation. While the rest of the industry may have been wrong-footed, he was convinced the plan was a solid contender.

“It wasn’t built on no thought having been given to it beforehand,” says Lowe. “I’ve been dealing with capacity at Heathrow in one form or another since the early 1980a. First, trying to get the right slots for Concorde and then I ran operations control for British Airways, when we were often constrained by these rather archaic rules at Heathrow.

“So I have looked at various ways and I thought of this idea a long time ago, but never really publicised it.”

It was only when the Coalition ruled out a third runway at Heathrow that Lowe thought it was time to act.

“The politicians said no third runway,” he says sipping coffee and still fighting jetlag. “That’s very clever then, because the solution then is to extend the runways you have got and use them better.”

Lowe mentioned his idea to a former colleague who just happened to live next to Steven Costello, an architect and transport planner who had worked on a number of international airports and who was close to Mark Bostock, a former engineer with Arup, who was at the time pushing plans to connect Britain’s biggest airport with the proposed HS2 rail project.

Lengthening a runway and effectively splitting it in two has never been done anywhere else in the world. Madrid Airport has the closest layout to what Heathrow Hub is proposing, but its design is closer to a “dog leg”, according to Lowe.

However, Bostock has “previous” when it comes to challenging the established view. He came up with the eventual design for High Speed 1, the rail line that connects London St Pancras station to Kent and the Channel Tunnel.

“We challenged British Rail and the establishment and the profession, arguing they had got the wrong alignment,” says Bostock. “There was no opposition to our proposition.”

The experience has so far been the same with Heathrow Hub, says Bostock. He acknowledges that when people first heard of the idea, the default position was sceptical.

But once they are talked through the scheme, which has been developed with the help of engineers at URS, Bostock says people acknowledge Heathrow Hub’s proposals are “technically sound”.

The plans include building a transport hub on a 200-acre site 3.5km north of Heathrow’s Terminal 5, which would include a new railway station on the Great Western Main Line and would connect to Crossrail from 2018. The transport “interchange”, as the group calls it, would also be directly accessible from the M25.

“Of course, when one comes in from the outside and you have got established airport groups, it’s obviously a little bit of a surprise when one comes up with a proposition that is technically sound,” says Bostock.

Heathrow Hub presented its ideas to a group of venture capitalists in October 2012 to help fund the scheme, which until that point had been developed with directors’ cash.

Its backers now include Ian Hannam, the former JP Morgan Cazenove banker, who was previously a civil engineer.

“I can genuinely see there is no real economic alternative to Heathrow,” says Hannam.

Heathrow Hub had originally proposed extending both the airport’s runways, but the commission ruled last week that there is the need for just one net new runway in the South East to meet demand by 2030. There may be a case for building a second in the London area by 2050, but Sir Howard said there would be insufficient demand to support two runways simultaneously.

The commission has asked for Heathrow Hub to develop its plans to extend the airport’s northern runway, which is 3,902m long, to the west.

The M25 would have to be bridged or diverted, but the scheme’s architects argue that at a cost of around £7bn, it is the simplest and quickest way to meet future demand.

By comparison, Heathrow has estimated the cost of building a separate third runway at £17bn, while Gatwick claims it can expand for £5bn to £9bn although the commission estimates this sum will likely be closer to £10bn to £13bn once surface access upgrades are included.

“Heathrow just happens to be the world-leading brand,” says Lowe. “And there we were talking about throwing it away. In any other business if you had a real market leader, why would you dream of doing anything other than expanding it?”

However, Heathrow Hub’s scheme has been described as the worse of two evils by local campaigners, who claim people who live under the flight path of the northern runway would receive no respite.

Heathrow uses one runway for departures and the other for arrivals. This pattern is changed halfway through the day to allow periods of quiet.

John Stewart, chair of the anti-Heathrow expansion campaign group HACAN, says an extended northern runway, which would be used for take-offs and landings, would mean no let up in noise. “You’d have a plane very probably every 90 seconds throughout the day,” he says.

Heathrow Hub argues that the impact would be less than HACAN and other groups calculate as both parts of the extended runway wouldn’t be operating at full capacity at all times. Aircraft could land on the westerly part of the extended runway during unsociable hours to reduce disruption for residents. No new areas would be affected by noise – unlike for Heathrow’s north-west runway, the group points out.

Lowe also believes that approach paths for aircraft landing at Heathrow could be better managed so that planes fly in several defined corridors, rather than all over central London. By the time construction work is completed, Lowe argues, aircraft will be much quieter due to improvements in technology.

However, Heathrow Hub now needs to win over more than locals. It is competing against Heathrow Airport’s own plans.

A spokesman for the airport said respite was a concern under the Heathrow Hub plans. The airport would have to assess the importance of respite for residents before it could formulate a firm view on the Heathrow Hub scheme.

Heathrow Airport would also have to agree a price. Heathrow Hub owns the patent for its extended runways idea.

“For the right price we’ll sell it to them, I’m sure,” Lowe smiles, adding that the sum is unlikely to be a “deal-breaker”. “Compared with the billions of pounds that we’re talking about, I think we’re not even talking to the decimal places,” he says.

The Davies Commission will publish the criteria against which it intends to judge the three shortlisted options – and potentially a new airport in the Thames Estuary if a further study order by Sir Howard into proposals backed by London’s Mayor, Boris Johnson, passes muster – in January.

Lowe and Bostock hope they will be able to work with Heathrow to hammer home the importance of an expanded hub, after Sir Howard last week said it struck him as “risky” to have “all of your eggs in one basket” at one, large airport.

Lowe and Bostock know what they are up against, but they are not deterred. “Heathrow is important,” says Lowe. “We have got to make sure that we don’t throw out the baby with the bath water.”