IMOLA, Italy - It's a muggy afternoon in early May and the air is thick with the fluffy white seeds from poplar trees. Flurries of the cotton-like substance float through the gates of the Autodromo Enzo e Dino Ferrari in Northern Italy and clump together in the shadow of the circuit's iconic race tower. Another storm should clear the air in the next hour or so, but in the meantime heavy clouds hang low over the terracotta roofs of the local neighbourhood.

Within the paddock, preparations are in full swing for the annual staging of the Historic Minardi Day. Despite the name, the two-day event is a celebration of all types of racing car, and on the eve of the opening morning the paddock is slowly filling with a heady mix of Ferraris, Alfa Romeos and (you guessed it) Minardis. Giancarlo Minardi -- the founder of the F1 team that once carried his name -- is the charismatic organiser behind this patchwork of nostalgia, and at the far end of the paddock he has organised some special guests. A fully-liveried Mercedes AMG Motorsports truck gives a hint at Sunday's headline act, but the name on the headrest still comes as a surprise...

Aldo Costa in the cockpit of the Mercedes W04. Laurence Edmondson

It's an odd quirk of modern Formula One cars that the individuals who design them rarely get to drive them. For all the hundreds of staff who work tirelessly to extract performance from one of these rare beasts, there's usually only two employees from each team who get to sit behind the wheel. But very occasionally events conspire to turn the usual order of things on its head, and last Sunday in Imola was one such occasion.

Aldo Costa has been Mercedes' engineering director since joining the team from Ferrari in 2011. The Italian mechanical engineer is not only one of the most successful car designers in the paddock, he is also one of the most charismatic individuals in Formula One. His sharp mind has contributed to two of the last three periods of dominance in the sport -- first with Ferrari between 2000 and 2004 and then with Mercedes between 2014 and 2017 -- and by all accounts he is still brimming with brilliant ideas. So when Mercedes needed a driver for its 2013-vintage W04 on Sunday at Imola, Costa emerged as the lead candidate.

The seeds of the opportunity were actually sowed during another Italian motorsport tradition the year before. The Mille Miglia -- once a fearsome 1,000 mile race from Brescia to Rome and back again -- now runs as a classic car rally and last May Costa and Mercedes team boss Toto Wolff shared a 1952 Mercedes 300SL Prototype on the journey. Over the course of the 1,000 miles the conversation naturally turned to a joint passion, and it was in that 1952 Mercedes that the plan started to develop.

"I spent four days with Toto together in the Mille Miglia, and you know in four days you speak quite a lot when it's just two of you in a car," Costa told ESPN on Sunday. "You talk about your favourite food, your life, your dreams ... and so it came out that we both like to test cars.

Aldo Costa-designed cars have won 11 constructors' championships. Mercedes/Steve Etherington

"I said I would like to test one of his cars and then later that year Mr Minardi, who was also organising the Lorenzo Bandini Trophy for Valtteri [Bottas], said to Toto, 'Can we have one of your cars for Imola?' The only problem was that we didn't have a driver and then Toto said, 'I've got a driver ... his name is Aldo Costa'.

"Giancarlo said 'What?!', but here I am. It's absolutely amazing!"

Wolff is known for his fastidious attention to detail and the perfect symmetry of the opportunity was too good to miss. Not only was the W04 the first car designed under Costa at Mercedes, but Minardi was the first F1 team to give him a job 30 years ago. From 1988 to 1995 Costa lived in the town of Faenza close to Imola and his apartment was just 50 metres from the main piazza where Bottas departed in an F1 car on Saturday to pick up the Bandini Trophy. Costa's return to his old hometown over the weekend brought happy memories of his early career flooding back.

"I worked for Abarth for a few months [after leaving university], but I was a fan of Formula One, so as soon as an opportunity came up I left the FIAT group to go to the very, very small team of Minardi. After one year, Mr Minardi saw how keen I was to design cars and gave me the responsibility together with an English aerodynamicist [Nigel Cowperthwaite] to be the chief designer. And then, just a couple of years later, I was the technical director! So at the age of 30 years old, I had found myself as the technical director of a Formula One team!"

Unlike the teams Costa worked for later in his career, Minardi was not known for its success in F1. In its 21 years in the category it never scored more than seven points in a season, but Costa's first car, the M189, scored two fifth-place finishes and two sixth-place finishes in 1989. Fittingly, a restored M189 was also among the cars Costa overtook while on track in the Mercedes on Sunday afternoon, no doubt resulting in a huge smile under his carbon-fibre crash helmet. But while those days at Minardi did not bring the silverware Costa later became used to, they did provide a vast amount of useful experience.

"In a small team you need to be so open to everything," he explained. "So at the time I was the one managing the data acquisition from the car, the one going in the wind tunnel and the one applying CAD and CNC machining systems for the first time at the team.

"The first Minardi done completely with the CAD/CAM was the 1989 car and it was my first car. I was the chief designer and they said, 'should we do it with the CAD/CAM?' and I said 'OK, let's do it with the CAD/CAM!'

Aldo Costa enjoys his engineering debrief with his Mercedes colleagues. Mercedes/Steve Etherington

"It was a success - much, much more precise and much better for the aero model, for sure. It was better, better, better everywhere, and when I left Minardi it was a team with CFD, a wind tunnel, simulation programmes and all the computer systems everywhere. So it was a small team but it had the makings of a more senior team, and of course it later evolved into Toro Rosso."

Costa made the move to Ferrari in 1995 and, keen to take on a factory-based role and reduce his travelling, started work on a project to turn the F50 road car into a Le Mans racer. Due to the politics surrounding sports car racing at the time, only three examples of the F50 GT were ever built and unfortunately the project was canned before it turned a wheel at a race meeting. But in the mid-1990s Ferrari was a company undergoing significant changes and Costa was moved to the F1 side of the operation to help rebuild the team's design office in Maranello. Since 1988, Ferrari's F1 cars had been designed in Guildford, Surrey under British technical director John Barnard, but Costa's job was to bring the design team back to Italy under the new technical leadership of Rory Byrne and Ross Brawn.

"I found myself reinventing and creating the design office in Maranello when they decided to reduce the Guildford office run by John Barnard and then, one year later, close it completely," Costa recalled. "So from a small design office, we again created a new design office and in 1996 and 1997 Ferrari ran a Barnard car that we were doing upgrades and subsystems for during the season, but it was not until 1998 that the first new car for Ferrari was built. In 1999 we won the constructors' championship and in 2000 to 2004 we won both titles five times."

When Byrne announced he would retire as Ferrari's chief designer at the end of 2006, Costa was promoted to replace him. Another drivers' title came in 2007 with Kimi Raikkonen at the wheel and a constructors' title in 2008, by which time Costa had been promoted to technical director. A major regulation change in 2009 caught the team off its stride and from that point onwards Maranello's title success has dried up. In 2010 it just missed out on the drivers' title at the final round in Abu Dhabi, but despite the near miss heads started to roll.

Aldo Costa worked for Ferrari from 1995 to 2011. Getty Images

"They asked me to step down as technical director and I didn't like any of the, let's say, opportunities they were showing to me and I decided to leave," Costa said. "The first ones to call offering me a job were Williams on the very same day, but after a month away from F1 I started talking with Ross [then Mercedes team principal] and we decided to start a new adventure there, which started in November 2011.

"Again, it was another further cycle of improving what was already there, keeping the good people and the good methodology and building on it to make it better and make better the organisation and the design for winning championships."

The W04 was the first Mercedes designed under Costa and scored three wins, eight pole positions and finished second to Red Bull in the 2013 constructors' championship. It provided a spring board for the four years of total domination that followed and now has a very special place in Costa's heart.

The Mercedes W04 in one of Imola's garages. Laurence Edmondson

"It's extra special to drive this car because it was my first one with Mercedes," Costa added. "And then coming here in the Minardi Day in Imola where it all started and yesterday when Valtteri's car fired up 50 metres from where I lived when I worked for Minardi, the very road where I lived and I spent so much of my life, it's like a big circle. Amazing!"

Costa was given two 30-minute runs in the W04 on Sunday, sharing the track with a mismatch of early '90s Ferraris, late '80s Minardis and even a Cooper from the early 1950s. The first of the two sessions was interrupted by red flags, including one just moments after Costa first engaged the W04's temperamental clutch to get the car rolling down the pit lane, but by the end of the first 30 minutes he had started to get a feel for the car.

"It was amazing," he said with a grin spreading across his face, "really, really amazing and an unbelievable experience. The car was really very easy to drive. All the systems were very easy -- with power steering, gearshift, the engine was brilliant, amazing brakes and tyres -- and you've got the feeling as a driver that you have got an infinite amount of performance and you are only using a hundredth of it.

"I had only really one lap at the end when I started to say 'OK, now I am settled in and now I start driving properly'. I did only one lap like that and I have infinite speed to find, and in every braking and in every acceleration I was so careful everywhere. But having said that, when I was overtaking one of the old cars, I got on the throttle coming out of the corner and the back end went sideways! I did a good oversteer catch and it was all very natural. I was proud of myself!"

Aldo Costa on track in the Mercedes W04. Laurence Edmondson

The second 30 minutes ran smoothly without a single stoppage and Costa remained on track for the entire session. He was clocked at 291km/h on the car's data recorder and by all accounts was not hanging around on either the corners or the straights. His fellow engineers climbed the pit wall to watch their man on track and returned to the garage with huge smiles on their faces. As the helmet came off, Costa was also grinning from ear to ear having achieved a lifelong ambition of driving one of the Formula One cars he'd designed. It really couldn't have happened to a nicer guy.