Winning one drivers? championship title is hard. Sustaining the motivation and performance necessary to do it all again the next year is even harder.
Sebastian Vettel successfully defended his first three titles but his crown finally slipped last year. Not only that, but for the first time since Jacques Villeneuve 16 years ago the defending champion failed to win a single race.
But Vettel at least managed to end the season among the top five in the drivers? championship. That?s something none of these drivers, who endured even more difficult title defences, managed to do.
1980: Jody Scheckter
Ferrari?s cup overflowed late in 1979. At home in Italy the scarlet 312T4?s crossed the line one-two, sealing the championship for Jody Scheckter with team mate Gilles Villeneuve runner-up in the points table.
However the team had one eye on the opposition, particularly the promise of Renault?s turbocharged engine, and had commenced work on its own turbo power unit. In the meantime the team?s venerable flat-12 engine remained in service for another year but the modifications made to it and the T4 chassis for 1980 spectacularly failed to bear fruit.
Short on downforce, lacking reliability and struggling with their Michelin tyres, the season was an unmitigated disaster. Defending champion Scheckter took a single points finish at Long Beach, soon decided to retire from the sport, and in his penultimate appearance failed even to get the wretched T5 on the starting grid.
Go ad-free for just £1 per month
1997: Damon Hill
Damon Hill won the championship with Williams in 1996 and the team produced another superb car the following year. Unfortunately for Hill he was no longer driving for them.
During Hill?s troubled 1995 campaign Frank Williams had already decided Heinz-Harald Frentzen would take his place for 1997. Upon his departure Hill came close to agreeing terms with McLaren but ended up driving for the win-less Arrows team.
When his car broke down on the way to the grid at the first race of the season it proved a depressing omen of what was to come. But the team?s new Bridgestone tyres occasionally proved the ace in their hand ? such as in Hungary where Hill sensationally passed arch-rival Michael Schumacher and was on his way to a dream victory.
But on the penultimate tour the failure of a minor hydraulic part caused his car to slow dramatically, and former team mate Jacques Villeneuve took the win from him.
1979: Mario Andretti
Having dominated the 1978 championship with the ground effect-harnessing 79 chassis, Lotus?s 1979 design took the concept to extremes in the pursuit of even more performance. But the radical Lotus 80 proved a failure.
On paper ? and in the wind-tunnel ? the 80 had promised immense levels of downforce. But the team couldn?t realise them on the race track without suffering severe ride and handling problems.
That wrecked Mario Andretti?s hopes of holding on to his championship. Indeed, Andretti scored more than half of his meagre points total that year while the team was still using the old car. By the end of the year they had abandoned the new car completely.
1961: Jack Brabham
Jack Brabham and Cooper cleaned up in 1959 and 1960 using a tidy rear-engined car which changed the course of F1 car development. But for 1961 a huge change in the regulations shook up the grid ? and Ferrari were better prepared than anyone.
With F1 engine capacities trimmed to 1.5 litres, Ferrari?s V6 engine easily outgunned the four-cylinder Coventry-Climax units used by Cooper. And so, having won five races the year before, Brabham never made it onto the podium in 1961.
He enjoyed more success away from F1, taking the rear-engined Cooper to the Indianapolis 500 where it performed promisingly. Within a few years, others had followed Brabham?s lead and conquered the 500-mile classic in similar cars.
1982: Nelson Piquet
Curiously, three-times world champion Piquet never finished in the top four in the season following any of his title wins. In 1982 the unreliable new BMW turbo engine in his Brabham was often the cause of his troubles.
The car was particularly ill-suited to the narrow Detroit street circuit ? that and an electrical problem in qualifying conspired to thwart his efforts to get the car on the grid.
But one week later in Canada he not only got the car through qualifying but he won the race as well. Another victory might have followed in Germany but he tripped over the lapped Eliseo Salazar. The reigning champion then threw punches and kicks at the bemused ATS driver.
The pain he experienced with BMW had its reward the following year however, when Piquet regained his title.
1985: Niki Lauda
Having pipped team mate Alain Prost to the 1984 championship, Niki Lauda remained at McLaren for a tilt at a fourth title the following year.
But he might as well have stayed at home as he suffered the most appalling unreliability. Lauda managed just three points finishes all season while Prost netted his first title.
The only saving grace for Lauda was a gritty final victory at Zandvoort, taken under immense pressure from his team mate.
1969: Graham Hill
Given the potency of the Lotus 49, Hill?s 1968 championship had been a close-run thing. Nonetheless when kicked off his title defence with second place in South Africa and his traditional victory in Monaco he looked quite capable of retaining his crown.
But that proved the last win of his career. As the season wore on Hill was increasingly overshadowed by new team mate Jochen Rindt. By the time they reached the penultimate round at Watkins Glen Hill had only added a further four points to his tally.
Then came the accident which almost ended his career. Having detached his seat belts following a spin, a tyre deflation caused him to lose control of his car again and Hill was thrown out of the car, suffering serious leg injuries.
1962: Phil Hill
Triumph and tragedy came hand-in-hand for Ferrari at the end of 1961. Phil Hill clinched the title on the day team mate Wolfgang von Trips was killed in a crash along with 15 spectators at Ferrari?s home race at Monza.
Then at the end of the year a group of top Ferrari staff quit the team following a dispute with founder Enzo Ferrari. Soon afterwards Hill had his own first-hand experience of the toxic politics at work in Maranello.
He brought the car home on the podium at the first three races of the year, but team manager Eugenio Dragoni was unimpressed with his efforts and gave a damning assessment of Hill?s driving to Ferrari by telephone.
Unmotivated and piloting a car increasingly eclipsed by the likes of BRM and Lotus, Hill failed to score in the remaining races. At the end of the year he joined the Ferrari deserters at the newly formed ATS team.
1988: Nelson Piquet
The 1988 season was a poor year for anyone who wasn?t driving a McLaren-Honda MP4-4. That went for reigning champion Piquet as well, even though he had moved from Williams to Lotus in order to keep the coveted Honda power beneath his right foot.
Despite having the same specification engines as McLaren, Lotus found their 100T was badly outclassed. At times they even failed to beat rivals who lacked turbo power.
Although Piquet began the year with a couple of podium finishes, later results called his motivation into question, including a series of spins and accidents. He was even out-qualified at Spa by Honda rent-a-driver Satoru Nakajima.
1966: Jim Clark
A major change in the engine regulations for 1966 caught several teams on the hop. Among them were Lotus, who were late to find a suitable engine for the new three-litre engine specification.
What they eventually obtained was a unit which utterly contradicted team founder Colin Chapman?s demands for simplicity and lightness. BRM?s 16-cylinder H16 was extremely complicated, not especially powerful and very heavy.
It was only thanks to inspired driving on Clark?s part that the failure-prone engine won a race, fitted to Lotus?s 43 chassis, in the penultimate race of the year at Watkins Glen.
The undefended titles
Alberto Ascari arguably set the banchmark for worst championship defences in 1954. He spent much of the year waiting for Lancia to debut their D50 grand prix car, and only appeared in four points-scoring rounds. That left him 25th at the end of the year with 1.14 points (for the story of how he scored one-seventh of a point, see here).
Two years earlier Juan Manuel Fangio had been forced to leave his first title undefended after suffering a neck injury at the beginning of 1952. He also stepped down from his final title defence two races into the 1958 season.
The driver who won the championship that year, Mike Hawthorn, announced his retirement at the end of the season, meaning the crown was undefended once more. Sadly Hawthorn was killed in a road accident just weeks later.
Tragedy also surrounded the circumstances of the 1970 champion, Jochen Rindt, who lost his life before the season ended and his title was confirmed.
Concerns over safety prompted Jackie Stewart to decided he would retire at the end of 1973, the year which produced his third world championship.
Only two other drivers declined to defend their titles: Nigel Mansell and Alain Prost after taking titles for Williams, in 1993 and 1994 respectively. Mansell opted to race in IndyCar after learning of Prost?s deal to join him at Williams, and Prost elected to cut his Williams deal short by a year as team principal Frank Williams was coming under pressure to hire Senna to drive alongside him.
Over to you
Which unsuccessful F1 title defences stand out in your memory? Which champions in other categories struggled to hold on to their titles?
And will Lewis Hamilton enjoy better luck defending his title this year than he did in 2009? Have your say in the comments.
F1 top tens
Read more top tens