Another birth from Glos BMD:
Child Surname Child Forename Mother's Former Name Year District Office Register Entry
HIGHLY Henry Mark BUTT 1870 Forest of Dean Westbury on Severn, Newnham 32 220

and marriage of parents:
Groom Surname Groom Forename Bride Surname Bride Forename District Parish Building Year Register Entry
HILEY John BUTT Julia Forest of Dean Monmouth Register Office Closed 1867 6 44

FreeBMD has this entry:
Marriages Dec 1867
BUTT Julia Monmouth 11a 84
HILEY John Monmouth 11a 84
HILEY Mark Monmouth 11a 84

Mike