Hi Floggle Toggle
Usually it is because the bride is a minor that they require parents permission to marry or stand surety; but in this case the marriage licence says that Avis is 27+ and James is 24+
I see the marriage took place 3 days later
Sussex Marriage Index:
Location: Rotherfield, East Sussex, Date: 2 Dec 1815:
Bride: Avis OVENDEN, spinster, of this parish
Groom: James MANKTELOW, bachelor, of this parish by licence
So in this case I do not know why!
Chris in 1066