This is the touching moment a step-dad officially adopted his 18-year-old stepson in a birthday surprise ceremony organised by the teenager.

Gavin McGeachie, 18, was gutted step-father Chris, 43, couldn't legally adopt him because he was no longer a child.

So instead Gavin and his mum Lyndsey, 40, organised a surprise for Chris' birthday, pretending to whisk him off for a posh meal.

Instead they set up a humanist unofficial adoption ceremony to cement the bond between the men, who have been close since Gavin was four-years-old.

Emotional footage of the do shows a confused Chris overcome with emotion when the penny drops.

The pair made vows to bond themselves as dad and son to each other forever and there was the symbolic handfasting.

Furniture upcycler Lyndsey, from Irvine, North Ayrshire, said: “Watching the ceremony, it melted my heart.

“One thing I always hoped for when I was a single mum was that I would meet someone who would take Gavin on as their own – and that’s exactly happened.

“Chris and Gavin have a good relationship which has only grown stronger over the years, and in the future they will cherish this memory.

“Since sharing the video it has become clear that there are lots of adults who are in the same position as Gavin, but this could be the beginning of a new type of ceremony.

“It is one where children can honour and acknowledge the parents who stepped up and raised them as their own."

Lyndsey said Gavin has "never looked at Chris as anything other than his dad" and they have never used the term 'step-dad' in their home.

Gavin wanted to surprise Chris with adoption papers on his 43rd birthday but quickly realised the law in Scotland limits adoption age to under 18.

With his mum's help, the contacted celebrant John Scott, who conducted their wedding yeas earlier.

They convinced Chris to meet them at a local restaurant for a dinner - and he was shocked to arrive and see their whole family waiting there, on August 21.

Chris had no idea why until John launched into a speech.

Lyndsey, mum to twins and another daughter, all eight, said: "I kept finding myself slipping up and almost giving the surprise away while we were planning it."

This video was filmed on the 21st August 2021.