Computer whizz Gary Rolf’s determination to help his gran overcome her deafness prompted him to come up with a simple device which could help millions.

Although his grandmother Bettie Rolf now has no hearing, he noticed that she followed TV subtitles during a family reunion at her Rochester home.

So he has designed a voice-activated computer app so she can keep up with everyday conversation with husband Bob via a screen.

Gary, 34, who lives with his wife Louise in Dubai, said:

“Bettie is now completely deaf, which makes communicating with her husband Bob and the rest of the family really difficult.

“It’s something that made me sad because she has always been very social and loves a good chat. She is still very chatty, but it’s hard to have a two-way flowing conversation.”

Gary, an arts director for an advertising firm, said he hopes the app, named Spuble, might help her dementia.

He said: “I think losing her hearing hasn’t helped her condition, because a lack of brain stimulation, including conversation, can accelerate the disease.”

“The Spuble uses speech-to-text technology to create live speech bubbles on a screen. This could be on a mobile phone or tablet.”

Gary and Louise, who are expecting twins later this year, joined other family members at the get-together for his grandparents’ 70th wedding anniversary at their home in Ajax Road.

He said: “When I saw her reading the subtitles on Coronation Street, I realised there might be a way to help.

“When I saw her reading the subtitles on Coronation Street, I realised there might be a way to help" - Gary Rolf

“Speech-to-text technology is commonly used today for things like Siri and other dictation apps, so I thought if I designed an interface that was simple, even my grandad Bob can use it and speak to her like he used to.”

He has put a film about Spuble on YouTube which shows Bob, 96, telling his childhood sweetheart how much he loves her.

He also asks whether she wants a cup of tea and she replies with a grin: “I’d rather have a pint.”

Bettie, 90, is an avid reader of newspapers and keeps up with current affairs and her favourite soaps. Bob said: “Gary is a good lad and always thinking of others, he has always been inventive.

"I’m sure this will make a difference, it must be frustrating for Bettie not being able to hear and join in a conversation.”

Spuble is now live on the Apple App Store.