Alfonso Antonio Vicente Eduardo Ángel Blas Francisco de Borja Cabeza de Vaca y Leighton

De Portago was born in London and educated in Biarritz, France. He was named after his godfather, King Alfonso XIII. His grandfather, the 9th Marquess of Portago, had been Minister of Public Instruction and Fine Arts and Mayor of Madrid. His father, Antonio Cabeza de Vaca y Carvajal, the 10th Marquess, was a prolific golfer and President of Puerta de Hierro who died of a heart attack after a polo match. His mother, Olga Beatrice Leighton, came from an Anglo-Irish family and was the widow of American financier Frank MacKey — founder of Household Finance Corp — who left her a fortune of $500 million. De Portago was fluent in four languages and spoke English with a distinctive British accent. He stood 1.83 m tall and weighed 77 kg. At age 17 he won a $500 bet by flying a borrowed plane beneath London Tower Bridge. He twice competed in the Grand National Steeplechase at Aintree as a gentleman rider, though keeping his weight down was a struggle.

De Portago entered motor racing in 1953 after meeting Luigi Chinetti, the Ferrari importer for the United States, who invited him to serve as co-driver in the Carrera Panamericana. By 1954 he was racing alone in a personal Ferrari Sport model at the 1000 km Buenos Aires. He won six major races in total, including the Tour de France Automobile, the Grand Prix of Oporto, and the Nassau Governor's Cup twice. Among sports car enthusiasts he was known as a "two-car man" for the frequency with which he burned out brakes, clutches, and transmissions, often requiring several cars to complete a race.

In 1955, during a sprint at Silverstone, de Portago was thrown from his Ferrari at 140 km/h after losing control on a patch of oil and was hospitalised with a broken leg.

He participated in five Formula One World Championship Grands Prix, debuting on 1 July 1956. His best result was second place at the 1956 British Grand Prix, a drive shared with Peter Collins. He scored a total of four championship points.

During the 1956 winter season in Nassau, de Portago steered clear of a crowd after the car ahead of him touched its brakes at 240 km/h, sending both cars into a 180-metre skid.

De Portago formed the first Spanish bobsleigh team for the 1956 Winter Olympic Games in Cortina d'Ampezzo, recruiting his cousins as crew. Having had only two or three practice runs in Switzerland before buying his own sleds, he steered the two-man bob to a fourth-place finish, missing a medal by 0.16 seconds. He was introduced to bobsledding by Edmund Nelson, an American from Beloit, Wisconsin, who later served as his navigator in the Tour de France Automobile win. In 1957 he won a bronze medal in the two-man event at the FIBT World Championships in St. Moritz.

On 12 May 1957, de Portago was killed during the 1957 Mille Miglia on a straight road section between Cerlongo and Guidizzolo, about 70 km from Brescia. He had been apprehensive about the event, citing the near-impossibility of knowing every corner and road condition over 1,000 miles of open public roads. A photograph dubbed "The Kiss of Death" shows him kissing actress Linda Christian at a pit stop shortly before the crash. A tyre burst on his third-place Ferrari 335 S at 240 km/h, sending the car into the crowd. The car hurtled over a canal and veered back across the road. De Portago and his navigator Edmund Nelson were both killed; de Portago's body was found beneath the wreck, severed in two. Nine spectators also died, including five children; two of the children were struck by a concrete highway milestone torn from the ground by the car.

Gregor Grant wrote of him: "a man like Portago appears only once in a generation, and it would probably be more accurate to say only once in a lifetime. The fellow does everything fabulously well." De Portago participated in five Formula One World Championship Grands Prix, earning four championship points. A "Portago curve" is named after him at the Jarama motor racing circuit in Spain. A second Portago curve is found at the St. Moritz-Celerina Olympic Bobrun, named in recognition of his foundation's efforts to renovate the lower portion of that track. Brazilian actor Gabriel Leone portrayed de Portago in the 2023 biopic Ferrari.

This article is based solely on the supplied corpus. No external sources were consulted; claims that could not be substantiated against the corpus were omitted under the drop-the-claim rule.