SIR Brian Souter’s investment vehicle is set for a windfall of nearly £160 million following the sale of Falkirk bus manufacturer Alexander Dennis Limited.

The businessman and his sister Ann Gloag, who co-founded Stagecoach, held the majority of shares in the Scottish bus maker through their respective investment vehicles.

ADL was sold yesterday to NFI Group, North America’s biggest bus and coach manufacturer, in a deal worth £320m.

The firm’s chief executive, Colin Robertson, said the deal preserves the jobs of the 2,600 staff employed by the firm in Falkirk. And he highlighted the cultural fit of the two businesses and the enhanced global growth prospects it has brought for ADL under its new parent company.

The acquisition is the first made by Toronto-listed NFI, which employs around 6,300 staff across Canada and the US, outside its native North America.

And it comes some 15 years after ADL had come close to going under. It was saved by a consortium including Sir Brian, Ms Gloag, Sir Angus Grossart and Sir David Murray after being caught up in the administration of then parent firm Transbus.

Sir Brian’s Souter Investments looks set to be the biggest beneficiary of the NFI deal. Based on its latest accounts, Souter Investments held a 49.53% stake in ADL, worth £158.5m based on the terms of its sale. Ms Gloag’s stake, held ultimately through Gloag Investments Group, was worth around £35m.

Yesterday’s deal valued the stake in ADL held by Nobel Grossart Investments, part of Sir Angus Grossart’s Nobel Grossart merchant bank, at £106.3m, while Mr Robertson’s shares were worth £19.8m.

ADL's primary shareholders, including Mr Robertson, have elected to roll around 10% of their transaction consideration into NFI shares.

Murray Capital, the family business of former Rangers owner Sir David Murray’s, sold its shares in ADL for £11.8m in 2014.

Mr Robertson declined to comment on windfalls for individual shareholders but said that if those investors “hadn’t ponied up back then I don’t know where we would be”. He said: “Fifteen years on, we have grown from £150m to £630m in sales, from 1,200 employees to 2,600, [and] from a UK-centric business to a proper international business, investing in excess of £25m a year in new products, engineering and marketing. Will they be getting a fair pay day? No doubt about that. But if you were marking their report card I would have to say I believe they have done more good than harm.”

The most recent accounts for ADL show that it made a pre-tax profit of £24.4m on turnover of £577m in the year ended December 31. Its sale comes as it continues to make headway in expanding sales overseas. While the UK accounts for around half of its business, some 25% of sales are now in Asia Pacific, including Hong Kong, Singapore, China and New Zealand. ADL has also been growing in North American, where it generates £100m of sales.

Mr Robertson, who will now lead NLI’s international operations from Scotland, said: “Clearly, the new company allows us to accelerate, to grow much faster in North America because of the resources that our new parent has on the ground there.”

Asked if the acquisition would have any impact on employees in Scotland, Mr Robertson said: “Absolutely not. This is where this is a fantastic deal, because if a [local] player was buying us there might be duplication of manufacturing capacity… but there is absolutely not.

“They are buying ADL, they are retaining the whole ADL company because, basically [with] our products, our markets, there is no overlap. If anything, they will invest time, energy, resources to even accelerate our five year plan.”

Paul Soubry, chief executive of NFI, said: “ADL is the UK’s number one bus manufacturer and the number one global producer of double-deck buses, with an established international presence and is recognised as a leader known for innovative products and a commitment to quality and service. We’re thrilled to have ADL join the NFI family.”