For on the very day that shares in the 125-year-old company raced to a nearly 20 per cent premium to value Gardner at pounds 16m, Mr McDonald also finally took control of debt-laden Sheffield United, the struggling First Division football club, after a bitter and protracted takeover battle.
The pounds 3.2m deal, rubber-stamped at a board meeting last Thursday, involved Mr McDonald and two anonymous backers buying a controlling 52 per cent stake in the club from the former owner, Reg Brealey, the controversial businessman behind the troubled jute processing company Titaghur.
"The negotiations were horrendous," says Mr McDonald. "Getting the shareholders to agree was bloody difficult."
Joining him on the new United board are his erstwhile rivals Stephen Hinchliffe, a local entrepreneur and former club director whose Facia group is now Britain's second largest private retailer, and Kevin McCabe, a Scarborough-based builder who made his fortune when he sold his pipes and cable-laying company to Southern Electric for pounds 11m two years ago. Both men also sought to wrest control of "the Blades" from Mr Brealey but were beaten to the punch by Mr McDonald.
The new board's task at Bramall Lane is daunting. The season got off to a woeful start when the manager, Dave Bassett, and the club's players and staff were not paid their monthly salary cheques.
United now languish third from bottom of the First Division and face an uphill struggle to avoid relegation, having lost 12 of 20 games so far. Gates have halved from an average of 20,000 two years ago, when United rubbed shoulders with the elite in football's top flight.
Last year, supporters fed up with the way the club was being run formed an action group, the Blades' Independent Fans' Association (Bifa) which accused Mr Brealey of denying the manager transfer funds and of stalling over a new stand. Bifa organised protest meetings and handed out red cards for fans to brandish at directors during matches.
Mr McDonald's credentials for reviving the club's fortunes seem as good as any. Unlike many football club owners, his connections with Pele's "beautiful game" are anything but tenuous.
"I've never been a golfer," he says, "but I've played amateur football at a decent level [he used to turn out for non-league Hyde United, the east Manchester club where he is now president]. I am a roots football person."
His background in the family scrap metal business and machine tools meant he forged close contacts across the Peak District with the city of Sheffield, the steel centre of the North. During the 1980s his Texas group, which retains majority control of L Gardner, became one of Britain's biggest independent foundries.
L Gardner itself is a recent addition, bought from the tractor-maker Massey Ferguson's offshoot Perkins two years ago, since when six-figure losses have been transformed into profits of pounds 1.8m in the year to August.
Nine in 10 of Hong Kong's 4,000 buses run on Gardner diesel engines, as do most of London's double-deckers, and leading customers for its engines and parts include such bus companies as Stagecoach and Leyland. "We are picking up orders left, right and centre," Mr McDonald says.
L Gardner was not the only turnaround situation he was attracted to. Two years ago he tried and failed to buy Premier League Manchester City, but pulled out of bidding when he realised the former City star Francis Lee was the popular choice among the side's long-suffering supporters.
"It was an 11th-hour decision," he recalls. "But without the fans' support, it is not easy to turn things round."
Undeterred, Mr McDonald soon turned his sights on Sheffield United - another big city club that has had to live under the shadow of a larger local rival.
"I hate to see underdogs," he explains. "Sheffield can carry two big clubs, and United should be on a par with Wednesday."
How much money he pumps into the club remains to be seen. Mr McDonald is reluctant to portray himself as a new Jack Walker, the steel magnate whose millions transformed the fortunes of Blackburn Rovers, who are the reigning Premier League champions.
"You've got to be very realistic. You don't make money out of football, it's not like a business. You do it for the enjoyment and seeing it grow."
Instead, he sees plenty of commercial opportunities off the field in merchandising, catering and corporate hospitality. But he is the first to recognise that only putting more bums on seats will restore the club's financial health.
"Gates are the problem. Being a Lancashire person, I don't really understand the Yorkshire people - I don't see the logic in fans staying away. Take Manchester City. They had a disastrous start to the season but their support remained very strong, averaging 28,000. But at Sheffield United it has halved in two years and we need 14,000 just to break even. That's a major, major concern because nobody can build success in any walk of life without having support. Very few people are a one-man band."
Mr McDonald reckons a return to home crowds of 20,000 at Bramall Lane would allow the club to sign big names and invest in the ground.
But he admits time is not on his side and wooing back Sheffield United's fairweather fans will not be easy. "Of course, there is a chicken and egg situation. We are pretty precarious at the bottom of Division One."