Whether the princess and Fayed were planning to marry is an important issue for the jurors, who must decide how the couple came to die on Aug. 31, 1997 in a car crash in a tunnel in Paris.
Fayed's father, Harrods' department store owner Mohamed al Fayed, contends that the impending announcement of an engagement was a reason why the couple was the target of a murder conspiracy directed by Prince Philip, husband of Queen Elizabeth II. Al Fayed also claims that Diana was pregnant with Dodi Fayed's child.
French and British police concluded that the driver, Henri Paul, was drunk and was driving too fast. He also died in the crash.
Al Fayed has said an engagement ring was selected by the couple in Monte Carlo earlier in August, and that the ring was collected from Alberto Repossi's jewelry shop near the Ritz Hotel in Paris on the evening before they died.
There is no dispute that a ring was purchased, but the jury will hear further testimony about whether Diana had accepted a proposal from Fayed and whether, as Mohamed al Fayed says, they intended to announce their engagement the following Monday the day after they died.
The video shown Thursday, taken by cameras at the Repossi shop, showed Fayed looking at several items during a visit of less than 10 minutes. He occasionally pointed at something in a display case, which was then brought out by staff.
Later, the assistant manager of the Ritz Hotel, Claude Roulet went back to the shop, collected several items and a brochure, returned to the hotel and made a note of the price of a "dis moi oui" ("tell me yes") ring 115,000 French francs, then equivalent to US$18,900.
A ring of that description was found in Fayed's flat after his death, jurors have been told.
Security cameras at the Ritz showed that Diana did not leave the couple's suite during the time Fayed and Roulet visited the shop.
Detective Inspector Paul Carpenter of the Metropolitan Police confirmed that a document was faxed from Repossi's shop in Monte Carlo to Ritz chairman Franz Klein, listing prices of three rings and four other items. The fax is dated Aug. 23, 1997, a day when Diana and Fayed were in Monte Carlo. Prices of three other rings and a bracelet were written on the back.