The unnamed sister-in-law raised eyebrows with the ‘over the top frock’ with some suggesting she ‘breached wedding etiquette’ as it was a similar colour to the bride’s dress.

A stunned guest at the ceremony shared a photo online of the group and said the outfit drama was “still a touchy subject” despite the wedding taking place almost three years ago in the Alps.

The picture shows the newlyweds stood near the groom’s sister in her posh frock, which she paired with long black gloves.