In a clip from the episode, provided exclusively to RadioTimes.com, Selina Cadell's Mrs Tishell tells Irene to listen to the Doc, but she says swimming is when she feels closest to her late husband.
Initially struggling to relate despite having lost a husband herself, Mrs Tishell then says that her husband "liked caravans, so whenever I see a caravan I think, 'Oh, Clive would have liked that.'" You can watch the clip right here, now.
Elsewhere in Wednesday's episode, Martin deals with the arrival of Jane, a herbalist who is giving her own ill-offered medical advice.
Martin is also recognised in the episode by a former girlfriend Sophie Trent, played by Hermione Norris, who invites him to present a recent paper he's written on geriatric pregnancies as keynote speaker at Imperial College in London.
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Meanwhile, PC Pinhole (John Marquez) inadvertently ends up having a fish pedicure when he tries to ask Janice on a date, and invites her round to the station with a romantic meal secretly prepared for them.
This season is set to be Doc Martin's last, with Clunes saying earlier this year that while "it is sad" it's also "the right time". He added: "I think everyone will probably appreciate it is time to finish. But it feels like a really good time to finish."
Doc Martin season 10 continues at 9pm on Wednesday 28th September on ITV. The series is also available to stream on BritBox – you can sign up for a 7-day free trial here. Looking for something else to watch? Check out our TV Guide.
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