Such authorised persons must be “properly dressed” with wigs and gowns as appropriate to their status absent which I have heard a judge chastise an unrobed solicitor attending at short notice. He made an exception and agreed to hear him speak.
A Litigant in person, is permitted to present their own case before a judge but the litigant may not be permitted to delegate this right to an agent if he is legally unqualified to act.
Not all judges adhere strictly to the rules and have discretion to allow exceptions.
An estate agent or letting agent may not be permitted to act other than as a Mckenzie Friend.
An agent may, however, with leave of the court (permission or at the invitation of the judge) be permitted to speak as a witness or to confirm rent arrears, breaches of tenancy agreement, etc.
Letting Agents cannot demand to be permitted to present a case, -this is for the discretion of the presiding judge to decide.
All this said, provided the litigant in person is physically present at court accompanied by the agent, then for expediency a judge is likely to allow the agent to present the case on behalf of the litigant landlord client – the judge need not permit it nor can the agent demand to be heard.
A judge could declare, “I cannot hear you” despite having perfectly good audible hearing.