"I thought the lad looked a bit young, but he was incredibly believable and we had no reason to doubt him," said Mr Earnshaw, a night-shift worker.
Now the couple are suing the Church of England after discovering their marriage was invalid, having been conducted not by a vicar, but by a well- meaning 18-year-old volunteer.
Ms Wilson and Mr Earnshaw, both 25, were told a week after the ceremony last autumn that they had been married by an unordained server at the church, who stepped in to take the ceremony after the vicar was late.
The vicar of St John's in Golcar, Huddersfield, was away and asked the Rev Robin Townsend, from a nearby parish, to step in.
The teenager - who has not yet been named and is now believed to be at university - was dressed in server's robes, similar to those worn by the vicar. When Mr Townsend failed to appear, he apparently took the decision to lead the ceremony.
When the vicar arrived - not having been told that the service time had been changed - he found the wedding under way. "I was told to be there at 2pm, but when I arrived the service had already started. I was shocked and surprised," Mr Townsend, vicar of Slaithwaite parish, said.
"Initially, I thought he was the new curate. He was wearing the correct dress. I didn't recognise him. When I found out what had happened, I was dumbfounded and shocked."
Because the youngster was not ordained, the marriage is neither legally nor religiously valid. The couple only realised something was amiss when they received an offer to have the service repeated free of charge.
But Ms Wilson, who works for a make-up company, said the biggest day of their lives had been ruined. "It is a day that we can never recreate. I couldn't believe it, we had worked so hard to make the day perfect."
The Bishop of Wakefield has launched an inquiry. His chaplain, Canon Roy Clements, said: "The Bishop is distressed for all concerned. He is not able to comment because it is likely to be subject to legal implications."