[7][b] He was the nephew of tennis player Count Pavel Sumarokov-Elston, who was his first coach and doubles partner, grandson of Count-General Felix Sumarokov-Elston, Governor of Kuban Oblast, and cousin of the infamous Prince Felix Yussupov, who later became known as one of the collaborators who conspired to kill Grigori Rasputin, cult leader and mentor of Empress consort of Russia Alexandra.

In his diary, Tsar Nicholas II wrote:"Today, Count Sumarokov, a young student, took part in the tennis - he is the best player in Russia.

"[14]He volunteered for the Russian Red Cross motorized ambulance unit at the outbreak of World War I,[15] and was assigned to the Black Sea Fleet.

[18] The family permanently emigrated from Russia in the midst of the Russian Revolution, which emerged from the social fallback of the World War.

[19][20] First they fled to Koreiz where they were joined by fugitive Felix Yussupov who had been freed from his house arrest due to his involvement in the Rasputin murder.

[1][8] They agreed to join the White Army, but General Anton Denikin refused the request because the princes had ties to the Imperial dynasty.

[18] They sailed to Malta on 13 April 1919 aboard the British battleship HMS Marlborough, which also transported several other Russian nobility exiles, including Empress Maria Feodorovna.

[26] At international level his first main tournament was the 1905 Bad Homburg Cup (of which he won the second-class edition) but lost in the second round to Irving Wright.

[1] Only a week after his first St Petersburg title Sumarokov traveled to Sweden to participate in the 1912 Summer Olympics with veteran player Aleksandr Alenitsyn.

[29] The Olympic draw suffered a setback on expected entries of well-known players due to scheduling conflicts with the 1912 Wimbledon Championships.

[31] The match, which was witnessed by Grand Duchess Maria Pavlovna had a back-and-forth fight so fierce that Sumarokov tore the strings of his racquet and had to change it but that could't save him from losing to the German in four sets.

[36] After Sumarokov took the first set 6-3 Kitson got frustrated, complained to the chair umpire, grabbed his towel and left the court citing a right hand injury, which resulted in a walkover home victory.

[37] 1913 started the same way as the year before: Sumarokov had to pass his University exams so he had few chances to practise before setting out to Paris for the World Hard Court Championships.

He was also eliminated from the doubles contest in the very first round mostly due to his partner Paul Aymé's leg injury, which he suffered the previous night and kept them handicapped the whole match.

[43] It had a star-loaded 136-competitor field with Frenchmen Maurice Germot, Max Decugis and British Arthur Lowe and Charles P. Dixon present.

[46] Although Sumarokov never played in the Davis Cup he represented Russia in the international matches against Great Britain and France in the last two consecutive years preceding the First World War.

[47] Sumarokov was still exhausted from his recent Russian Championships final with Dixon and thus lost easily to Lowe and decided to step back from further participation and had to be replaced with inexperienced players.

Curiosity of the Russian-German meeting was that the Sarajevo regicide happened during the tournament (which later escalated into World War I) and Russia had sent an envoy to France to strengthen a possible alliance against the German Empire.

It was agreed to follow Davis Cup rules and the French delegation was an all-Olympian squad of Maurice Germot, Max Decugis, Albert Canet, Édouard Mény de Marangue.

[1] The following year he clinched his first French title at the South of France Championships beating home favorite Alain Gerbault in a five-set final.

[54] He defended the South of France title for the second time against legendary Henri Cochet having beaten Charles Aeschlimann on his way to the final.

[55][3] At the same tournament he also repeated his previous year's feat with Lenglen by overcoming Lord Rocksavage and Elizabeth Ryan in the mixed final.

de Nice George Lyttleton-Rogers and his partner Rosie Berthet had an overwhelming victory over Sumarokov and Miss J Franks in the mixed final.

[58] Later he adjusted his game to putting a curl to the ball as well as hitting it hard and with a high trajectory as described by Henri Cochet in his book Tennis.