Question: What was the middle name of the pianist who first performed Prokofiev's Piano Sonata No. 8?

Context paragraphs:
Piano Sonata No. 3 (Brahms): The Piano Sonata No. 3 in F minor, Op. 5 of Johannes Brahms was written in 1853 and published the following year.  The sonata is unusually large, consisting of five movements, as opposed to the traditional three or four.  When he wrote this piano sonata, the genre was seen by many to be past its heyday.  Brahms, enamored of Beethoven and the classical style, composed Piano Sonata No. 3 with a masterful combination of free Romantic spirit and strict classical architecture.  As a further testament to Brahms' affinity for Beethoven, the Piano Sonata is infused with the instantly recognizable motive from Beethoven's Symphony No. 5 during the first, third, and fourth movements.  Composed in Düsseldorf, it marks the end of his cycle of three sonatas, and was presented to Robert Schumann in November of that year; it was the last work that Brahms submitted to Schumann for commentary.  Brahms was barely 20 years old at its composition.  The piece is dedicated to Countess Ida von Hohenthal of Leipzig.

Piano Sonata No. 7 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 7 in B♭ major, Op. 83 (1942) (occasionally called the "Stalingrad") is a sonata composed for solo piano, the second of the three "War Sonatas".  The sonata was first performed on 18 January 1943 in Moscow by Sviatoslav Richter.

Emil Gilels: Emil Grigoryevich Gilels (sometimes transliterated "Hilels"; , Russian: Эми́ль Григо́рьевич Ги́лельс , "Emiľ Grigorievič Gileľs "; 19 October 1916 – 14 October 1985) was a Soviet pianist, widely regarded as one of the greatest pianists of the 20th century.

Piano Sonata No. 9 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 9 in C major, Op. 103 (1947) is a sonata for solo piano composed in 1947 and consists of four movements.  The sonata was dedicated to Sviatoslav Richter, a member of the Union of Soviet Composers, and by whom it was first performed on 21 April 1951 in Moscow.

Piano Sonata No. 6 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 6 in A major, Op. 82 (1940) is a sonata for solo piano, the first of the Three War Sonatas.  The sonata was first performed on 8 April 1940 in Moscow.

Piano Sonata No. 5 (Prokofiev): Sergei Prokofiev's Piano Sonata no. 5 in C major, Op. 38 (1923) and Op. 135 (revised 1952-53) is a sonata for solo piano.  Prokofiev composed the sonata in Ettal, by the Bavarian Alps, and dedicated it to Pierre Souvtchinski, a musicologist and friend.  Even though the revised version of the sonata has a new opus number, if one compares the two versions closely, there are few radical differences between the two, with most of the changes occurring in the last movement.  This sonata was the only piano piece of this genre to be composed during his life outside of Russia.

Piano Sonata No. 1 (Vine): The Piano Sonata No. 1 of Carl Vine was composed in 1990 and dedicated to Australian pianist Michael Kieran Harvey, who made the debut recording of the sonata under the Tall Poppies label in 1991.  The first printed edition, under the label Chester Music, bears the following description: "A complex and challenging piano sonata composed by Carl Vine for the Sydney Dance Company in 1991.  The piece was first performed by Michael Harvey in North Melbourne in June 1991.  The music is full of rich chordal movements, unusual flowing harmonies and tonalities, with great extremes of dynamic and energy.  Reflecting the physical origins of the piece as a dance, the music is dotted with very strict changes of tempo which require exact adherence, rather than the Rubato approach that typifies many piano interpretations."  The work is in two movements, the second of which bears the marking "Leggiero e legato".

Piano Sonata No. 15 (Beethoven): Piano Sonata No. 15 in D major, Op. 28, is a piano sonata by Ludwig van Beethoven.  The name Pastoral or Pastorale became known through A. Cranz publishing of Beethoven's work, but was first coined by a London publisher, Broderip & Wilkinson.  While not as famous as its immediate predecessor, Piano Sonata No. 14, it is generally admired for its intricate technicality as well as for its beauty.  The sonata takes roughly twenty-five minutes to play with its intended repeats.

Piano Sonata No. 3 (Beethoven): Ludwig van Beethoven's Piano Sonata No. 3 in C major, Op. 2, No. 3, is a sonata written for solo piano, composed in 1795.  It is dedicated to Joseph Haydn and is often referred to as Beethoven's first virtuosic piano sonata.  The three Opus 2 sonatas all contain four movements each, an unusual length which seems to show that Beethoven was aspiring towards composing a symphony.  It is both the weightiest and longest of the three Opus 2 sonatas, lasting over 25 minutes, presenting many difficulties, including difficult trills, awkward hand movements, and forearm rotation.  It is Beethoven's second longest piano sonata in his early period, only to Beethoven's Grand Sonata in E-flat Major, Op. 7, published a year later.

Piano Sonata No. 8 (Prokofiev): Sergei Prokofiev's Piano Sonata No. 8 in B♭ major, Op. 84 (1944) is a sonata for solo piano, the third of the Three War Sonatas.  The sonata was first performed on 30 December 1944 in Moscow by Emil Gilels.

Supporting paragraphs: Piano Sonata No. 8 (Prokofiev) Emil Gilels
Answer: Grigoryevich