Lawyers for the Beaverbrook Art Gallery have started their closing arguments in an arbitration into millions of dollars worth of disputed works of art.

They are fighting a British foundation controlled by Lord Beaverbrook's descendants for ownership of 133 paintings.

The gallery says the paintings were gifts to the people of New Brunswick, but the foundation says they were only on loan to the gallery.

Gallery lawyer Larry Lowenstein says Beaverbrook himself decided to lend paintings, but only after he'd already given many of them as gifts.

On Monday, Lowenstein said one of the most important facts in the case is a 1960 change to the trust agreement that created Beaverbrook's foundation.

Lowenstein says the change was a watershed because it allowed the foundation to begin lending paintings. He says that proves that before the change was made, the foundation could not lend paintings, it could only give them as gifts.

Eighty-five of the disputed paintings were sent to the gallery in Fredericton before the change. Lowenstein says that means they could not have been loans.

He also argued that one of the foundation's own expert witnesses ended up bolstering the gallery's case.

Accountant Will Kenyon testified about the foundation's records and what they said about ownership.

Lowenstein says Kenyon never produced a single piece of evidence proving the loan of any paintings before 1960, and he said Kenyon acknowledged the records say nothing either way about Lord Beaverbrook's intentions.

Lowenstein says other facts that have emerged in the arbitration hearing support his argument that something changed in 1960.

A former gallery employee testified that the label "property of the Beaverbrook Foundation" was only added to the paintings sometime after he left the gallery in March 1960.

Six months after that, Lord Beaverbrook's London secretary came to the gallery to update the paintings' ownership records.

Acting on his orders, she destroyed earlier versions of records, so it's a mystery whether they indicated the paintings were gifts or loans.

Lowenstein says given the secretary was working for the foundation when she destroyed the records, it should be up to the foundation to prove they would have supported the theory they were loans.

The gallery will take about a week to lay out its closing arguments. The foundation will take roughly the same amount of time next week.