Royal Liverpool Philharmonic Society (RLPS) said they were basing their claim that the Royal Liverpool Philharmonic Orchestra (RLPO) were "the UK's oldest surviving professional symphony orchestra" on the entire orchestra being professional from 1853. They said this was five years before the Hallé Orchestra (Hallé) gave its first concert in 1858. They said the claim was made as the result of the recent cataloguing of their extensive archive, which had previously been un-catalogued and inaccessible. RLPS said that prior to this review of their archive the conventional wisdom in classical music circles was that Manchester's Hallé was the UK's oldest surviving professional symphony orchestra. It was believed that the RLPO was essentially an amateur organisation whose players were provided by the Hallé. RLPS said they believed these claims were made without proper reference to the documentary evidence contained within their archive. RLPS provided a book on their history, The Original Liverpool Sounds: The Royal Liverpool Philharmonic Story by Darren Henley and Vincent McKernan (2009) which supported the above and stated "the documents in the Royal Liverpool Philharmonic's archives suggest that the RLPO has a far stronger claim to this title than their colleagues in Manchester."

RLPS provided copies of documentary evidence that they said supported its claim that the Orchestra has consisted of professional members since 1853, rather than since its inception in 1840. These included 35 letters from orchestral players in 1850 in which they agreed to accept the terms offered by RLPO for the coming season. They said this showed RLPO was appointing its orchestra on an annual basis from an early stage. They also provided Committee minutes which they said also showed this.

RLPS provided their annual accounts for the years 1853–1858 and said these showed their expenditure for payment of the players was approximately one-third of their total expenditure, and that this would not be the case if the Orchestra was not professional. They said this was similar to their expenditure on players today. They also provided accounts for a number of years up to 1939, when Liverpool City Council took over the running of the orchestra, which they said showed this expenditure was consistent.

RLPS said their archive of concert programmes also strongly supported their claim. They said these provided a continuous record, year after year, of the names of professional players who have played with the RLPO. They said non-professional players were denoted with the words "And Amateurs" at the end of each orchestral section. They said the last time this wording was used was in a November 1852 concert programme, and that the words do not appear in any programmes since, up to the present day. They said the programmes also demonstrated a strong continuity of players in the Orchestra and that most of the same players were employed year after year. They said this demonstrated that the RLPO was a body with a distinct identity and recognisable set of players associated with it.

RLPS did not believe that the RLPO was, in its early days, simply made up of members of the Hallé Orchestra. They provided evidence of players who appeared for the Hallé in its first year, 1858, and said that many of these had previously appeared for the RLPO. They said it could therefore be argued that it was the Hallé which was made up of members of the RLPO, rather than the other way around. The RLPS also said that the practise of orchestras sharing players but maintaining their own identities had been in existence since the formation of both the Hallé and RLPO, and continues today. They provided a number of examples of modern players and leaders of orchestras who also play for more than one orchestra.