Sir Henry Irving (6 February 1838 - 13 October 1905), born John Henry Brodribb, sometimes known as J. H. Irving, was an English stage actor in the Victorian era, known as an actor-manager because he took complete responsibility (supervision of sets, lighting, direction, casting, as well as playing the leading roles) for season after season at the Lyceum Theatre, establishing himself and his company as representative of English classical theatre. In 1895 he became the first actor to be awarded a knighthood, indicating full acceptance into the higher circles of British society. Irving is widely acknowledged to be one of the inspirations for Count Dracula, the title character of the 1897 novel Dracula whose author, Bram Stoker, was business manager of the theatre.

After a few years' schooling while living at Halsetown, near St Ives, Cornwall, Irving became a clerk to a firm of East India merchants in London, but he soon gave up a commercial career for acting. On 29 September 1856 he made his first appearance at Sunderland as Gaston, Duke of Orleans, in Bulwer Lytton's play, Richelieu, billed as Henry Irving. This name he eventually assumed by royal licence. When the inexperienced Irving got stage fright and was hissed off the stage the actor Samuel Johnson was among those who supported him with practical advice. Later in life Irving gave them all regular work when he formed his own Company at the Lyceum Theatre.  For 10 years, he went through an arduous training in various stock companies in Scotland and the north of England, taking more than 500 parts.  his delineations of the various characters (...) were admirably graphic, and met with repeated rounds of applause. Possesed of a fine voice, which he modulated with great taste and judgment, he was able to mark the depth or frivolity of the character he was representing with remarkable facility.  He gained recognition by degrees, and in 1866 Ruth Herbert engaged him as her leading man and sometime stage director at the St. James's Theatre, London, where she first played Doricourt in The Belle's Stratagem. One piece that he directed there was W. S. Gilbert's first successful solo play, Dulcamara, or the Little Duck and the Great Quack (1866) The next year he joined the company of the newly opened Queen's Theatre, where he acted with Charles Wyndham, J. L. Toole, Lionel Brough, John Clayton, Mr. and Mrs. Alfred Wigan, Ellen Terry and Nellie Farren. This was followed by short engagements at the Haymarket Theatre, Drury Lane, and the Gaiety Theatre. Finally he made his first conspicuous success as Digby Grant in James Albery's Two Roses, which was produced at the Vaudeville Theatre on 4 June 1870 and ran for a very successful 300 nights.  In 1871, Irving began his association with the Lyceum Theatre by an engagement under Bateman's management. The fortunes of the house were at a low ebb when the tide was turned by Irving's sudden success as Mathias in The Bells, a version of Erckmann-Chatrian's Le Juif polonais by Leopold Lewis, a property which Irving had found for himself. The play ran for 150 nights, established Irving at the forefront of the British drama, and would prove a popular vehicle for Irving for the rest of his professional life. With Bateman, Irving was seen in W. G. Wills' Charles I and Eugene Aram, in Richelieu, and in 1874 in Hamlet. The unconventionality of this last performance, during a run of 200 nights, aroused keen discussion and singled him out as the most interesting English actor of his day. In 1875, again with Bateman, he was seen as the title character in Macbeth; in 1876 as Othello, and as Philip in Alfred Lord Tennyson's Queen Mary; in 1877 in Richard III; and in The Lyons Mail. During this time he became lifelong friends with Bram Stoker, who praised him in his review of Hamlet and thereafter joined Irving as the manager for the company.

Using a quote from the above article, answer the following question: What was his biggest achievement during the early years?
Possesed of a fine voice, which he modulated with great taste and judgment, he was able to mark the depth or frivolity of the character he was representing