All births in England, Wales and Northern Ireland must be registered within 42 days of the child being born. PC Joe Penhale (John Marquez) reminds Martin (Martin Clunes) & Louisa (Caroline Catz) of this law.
Martin Clunes (Dr. Martin Ellingham) & Julie Graham (Maggie Reid) also worked together in William and Mary (2003) as William Shawcross & Mary Gilcrest respectively.
Rory Wilton plays Chippy Miller in this episode and a further six. He earlier played the part of Mr Hubble in episode 5.1, Preserve the Romance (2011).
Martin Clunes began working on Doc Martin at the same time he'd been already part of the series William and Mary, which he starred in with Julie Graham (as the titular William and Mary), who plays Maggie Reid (PC Penhale's estrange wife) here.