Born on 4 February 1913 to wealthy parents, Seaman fell in love with cars as a schoolboy. He would spend endless hours drawing pictures of racecars including a Seaman Special. As soon as he was old enough to get a license his parents bought him a Riley sports car and later replaced it with a MG Magna. Seaman was enrolled in Cambridge at this time but his heart was in cars. He entered several local races with minimum success. In 1934 he returned from school and announced to his distressed parents that he would not be going back. Instead he was joining Whitney Straight and his racing team. He purchased Straights MG Magnette and set off for the continent making his debut in the GP de LAlbigeois where he promptly stalled on the grid. The next race was a Voiturette event, which preceded the Coppa Acerbo. On that difficult 36-km circuit he finished a commendable 3rd place. His first victory came in a support race leading up to the Swiss Grand Prix where he started from the ninth row of the grid to take the lead on the 11th of 14 laps. His victory was marred by the death of his teammate Hugh Hamilton.
Seaman was supported all the while by his reluctant mother who had taken over the families finances due to the ill-health suffered by his father. His father died on 3 February 1935 and for the rest of his life there would be battles with his mother, first over his racing and then over his marriage. Seaman meanwhile had purchased an ERA but found the Bourne outfit unable to support his car effectively. He decided that he needed to establish his own team. The most important person in this new team was Giulio Ramponi who used to work for Alfa Romeo and knew everything there was to know about a racecar. The effect was immediate and Seaman began a string of victories that brought him to the attention of the factory teams. For 1936 Ramponi recommended that Seaman purchase a 10 year old Delage from Earl Howe. Feeling that the car was obsolete he was incredulous at first but Ramponi saw in the car the potential to dominate the 1500 cc class. Howe was more than glad to sell the car and all the spare parts that he had. Ramponi went to see Monsieur Lory at Delage and was given plans and some new parts to bring the Delage up to date. The car was stripped and modified extensively. One of the strengths of the car in addition to its drivability was its fuel consumption, which allowed it fewer pitstops than the opposition.
The car and driver were the sensation of the 1936 season and awaiting him upon his return to London was a telegram from Daimler-Benz requesting his attendance at an upcoming driver-trial at the Nurburgring. Seaman impressed Alfred Neubauer with his fluid driving style and was asked to return for more tests. Seamans mother was concerned as he was regarding the political implications of an Englishman driving for a German team. He sought advice from friends at the RAC as well as Earl Howe. They told him that this was an opportunity that should not be passed up and that if things got worse he could always resign. In December he signed a provisional contract for 1937 subject to the approval of Adolf Hitler which would be given.
His debut race was in Tripoli where he lay 2nd to Lang prior to suffering supercharger trouble which dropped him to seventh. Seaman became a popular member of the team because of his honest, straightforward character. Neubauer took a strong liking to the young driver. Seamans first year with Mercedes was solid if not spectacular. The mechanics were impressed with his mechanical knowledge, which he relayed through Rudolf Uhlenhaut, who spoke fluent English. 1938 marked the beginning of the new 3-liter formula and because he was still the junior driver on the team a new car was not ready for him until the German Grand Prix in July. During his forced "holiday" he met his future wife Erica Popp whose father was President and co-Founder of BMW. Seamans mother was at first friendly to the young German girl until she found out that her son intended to marry this girl. She was violently opposed to the marriage, more for the problems she felt that her son would encounter for marrying a very young German girl than for any personal animosity she had towards her. Sadly Seaman became estranged towards his mother until his death.
Finally the German Grand Prix arrived. For this race the Mercedes team had no fewer than seven of the new W154s during practice. Seaman was quick to shake off any rust and was third fastest during qualifying. Seaman was second to von Brauchitsch until his German teammate suffered a car fire during a pitstop. Seaman assumed the lead that he would hold until the end. This victory would mark the highpoint of his career for an Englishman on the victory podium of a major European race was still a rare thing, the fact that he was driving a Mercedes in Hitlers Germany made it rarer still! The next race that he drove in was the Swiss GP where he came in a fine second to Caracciola. After another successful season that saw him win his first race he was re-signed for the 1939 season. At the opening race he had to stand down, as there were only two new cars ready. The next race, the Eifel GP ended seconds after it began for Seaman when he suffered a failed clutch. Going to Spa in Belgium, Seaman was determined more than ever that he should no longer be considered a junior or reserve driver. The race was run in a downpour and on lap nine even the regenmeister Caracciola spun. On the tenth lap Seaman took the lead while the rain had stopped. With the track both wet and dry at various places experience would have told the driver that this condition could be the most dangerous. Seaman could only think of the first two races of the year and was out to prove that he was second to none on this or any other team. At La Source Seamans car went into a skid and left the track, crashing sideways into a tree. The drivers compartment had been damaged and as the car burst into flames the driver was trapped. Two Belgian officers pulled the driver clear but he was to die from his burns just after midnight. Neubauer would relate in his memoirs that it was a familiar story. Ninety-nine times a driver takes a bend at precisely the same angle and precisely the same speed. Then the hundredth time he wants to go one better, to cut one second off his time and puts a shade more pressure on the accelerator. That shade is fatal.
At his funeral were representatives of both Mercedes and Auto Union and the board of directors at Mercedes decreed that in all of the display windows of their dealerships would be placed a portrait of the only driver ever to be killed driving one of the Silver Arrows.