Jackie 'O' Henderson's bestie Gemma O'Neill raised concerns about Kyle Sandilands months before on-air fight

Jackie 'O' Henderson's best friend and manager, Gemma O'Neill, raised concerns about Kyle Sandilands' alleged behaviour towards the radio star five months before their explosive on-air fight brought their long-running show to an end.

As Henderson, 51, prepares to take on former employer ARN in an $82million Federal Court battle next month, her legal team is seeking access to 'all records' relating to the events that led to the on-air blow-up, according to The Australian.

That includes complaints O'Neill made in October last year about Sandilands' alleged behaviour towards Henderson, months before their on-air falling out resulted in both of their $100million contracts being terminated. 

The move is part of a larger legal bid from Henderson's lawyers to access 'documents created in relation to, or as part of, the investigation conducted by' ARN chief people officer Ros Reeves and content boss Kerri Elstub.

They are also seeking access to 'documents recording the assessment, control measures, and other measures to eliminate or minimise risks to the health and safety of workers at (ARN) created by Mr Sandilands'.

Sandilands launched an on-air tirade at his co-host on February 20, prompting Henderson to take several weeks of leave before the show was ultimately axed and both presenters' contracts were terminated.

Last week, it was reported that Sandilands will be required to provide text messages and emails he exchanged with his former radio co-host, as she takes on their former employer.

Sandilands was ordered to produce any communications exchanged with Henderson, as well as messages and emails concerning her, during the breakdown of their relationship before ARN ended their breakfast show, The Australian reported.

The shock jock has also been subpoenaed to appear as a witness in the case.

Henderson is suing her former employer for unfair dismissal, alleging ARN took unlawful 'adverse action' against her after she raised concerns about Sandilands.

Sandilands has already settled his own legal dispute with ARN after launching an $85million lawsuit against the company.

The broadcaster reached a reported $12million settlement with ARN after negotiations with former chief executive Ciaran Davis. 

As part of that earlier legal battle, Sandilands provided the Federal Court with a detailed first-person account outlining the deterioration of his relationship with Henderson.

ARN was recently granted permission to rely on that account in defending Henderson's claim.

The company has also been granted access to a court-ordered medical examination Henderson underwent with clinical psychologist Dr Justine Corry, along with material produced in response to a subpoena issued to Dr Emma Agnew. 

Further private communications could also become part of the case.

Henderson's manager, Gemma O'Neill, and veteran entertainment reporter Peter Ford were subpoenaed to produce documents more than three weeks ago, with ARN expected to seek access to any material they provide to the court. 

The evidence could shed further light on the events surrounding the breakdown of Henderson and Sandilands' relationship and the circumstances leading up to ARN's decision to terminate the breakfast program.

The Federal Court proceedings are expected to involve evidence from several key figures involved in the long-running dispute, including Sandilands himself.

Last month, an emotional Sandilands revealed he was left in tears after learning Henderson had been diagnosed with post-traumatic stress disorder.

As Henderson battles her former employer in court, her PTSD diagnosis was referenced in a medical report prepared by Dr Jonathan Phillips. 

The radio king later expressed his disbelief at allegations contained in court documents, saying they bore little resemblance to his recollection of events and had left him deeply hurt.