A family in Nether Woppington has postponed telling their grandmother how old she has become, holding back the news for two weeks while a filming schedule was drawn up and a cousin's newly purchased telephone charged, relatives confirmed on Thursday.

The grandmother, Mrs Edith Brankworth, turned ninety on 14 October. She was informed that the number could not be disclosed to her until the family had agreed a schedule for capturing the reaction of every descendant individually, since a single announcement would provide only one piece of footage.

"We wanted it to feel spontaneous, and spontaneity requires that nothing be left to chance," said her grandson Marcus Brankworth, who is directing the project and has assumed responsibility for continuity. "If we simply told her in the kitchen, we would have one shot and no coverage."

The schedule

Under the arrangement, each of Mrs Brankworth's eleven descendants will be filmed in a separate room of the family home while being told the number of years she has been alive. The clips will then be posted to a shared family channel whose name references the grandmother by her first name.

Mrs Brankworth herself occupies the final slot, in which she will at last be informed of her own age and asked to respond. The family has requested that she appear more surprised than she managed during a rehearsal conducted on Tuesday.

"She simply said 'ninety' and carried on peeling the potatoes, which will not perform," said Marcus. "We've asked her to consider dropping the peeler and embracing the moment."

The reshoots

An uncle, Gerald Brankworth, was filmed on Monday and has formally requested a second take, explaining that he had blinked and briefly thought about something else. The request has been granted, and he has been pencilled in for Sunday, when the light in the back room is considered more forgiving.

A great-niece currently travelling abroad has been given the number in advance so that her reaction can be filmed in front of a waterfall, which she will pretend to be hearing for the first time. "The waterfall window is quite narrow," said Gerald.

Mrs Brankworth, who has not officially been told she is ninety, observed that she had in fact been told. "They put it on a birthday cake," she said. "I can read. Are they eating the cake or not?"

The family confirmed the cake is being held back for a group photograph at the end of the shoot, for which no date has been set, owing to weather over the waterfall.