The following extract is from the BBC report of the hearing. For full article click here.
The judge is to decide whether Cardiff City has a strong enough defence to go to trial or rule in Langston's favour without the need for a full trial.
Langston want the court to make a summary judgement that would see Cardiff City facing a bill to repay £24m of the £31m immediately.
However, the club's lawyers have argued that the dispute should go forward to a full trial.
It claims the loan is not repayable until 2016 and it could face an uncertain future if it lost the case.
Following the two-day hearing, Mr Justice Briggs said he would take time to consider his ruling.
At the start of the hearing, Langston's counsel, Michael Driscoll QC had said: "It is common ground that the claimant loaned £24m to the club in 2004 and is yet to be repaid.
"The club says that nothing is to be repaid at this time, and the question is whether there is enough in what the club says to justify this case going to trial.
"The claimant says that there is nothing in what the club has said."
The club said that a variation to the loan agreement in 2006 means the loan is not repayable until 2016.
However, Langston claimed in court that so many changes had been made to the contract that this agreement no longer stood.