The episode, which was directed by Guillem Morales, follows the story of David, played by Shearsmith, a middle class stay-at-home dad, who happens across a lone black shoe.

9 was announced in October 2015, and heavily publicised in January 2016, at which time Keeley Hawes and Mathew Baynton were named as guest stars in the series.

[5] Shearsmith identified David as one of his favourite characters from the series, and said that he fondly remembered working with Hawes, whom he praised as a performer.

9, the episode's script, and Morales's direction, expressing how much she had enjoyed working with Pemberton and Shearsmith, as well as the amount she had laughed during the filming process.

David keeps an eye on the shoe, and, by the time Louise arrives home that evening, has moved it to the dinner table.

Later, in daytime, David chastises Sally for playing with the shoe, and Louise is angry that he has hung posters advertising his find that feature their phone number.

David's multimedia campaign and reward offer, initially unsuccessful, ultimately result in a visit from a young man who has a matching shoe.

Once satisfied by his account, and having spent a final few moments alone with the newly matched pair, he reluctantly hands it over, holding back tears.

Sally and Louise are happy in the kitchen, when David, smartly dressed and with a confident manner, returns from work.

Over the credits, security footage from 15 March 2016 shows David placing the shoe outside his house before jogging away.

[16] The comedy critic Bruce Dessau identified "stories of men who marry their VW Golfs or women who fancy the Eiffel Tower" as something he initially thought an inspiration, and noted The Good Life as a potential influence for David and Louise's lifestyle.

[9] The episode uses Vivaldi's The Four Seasons to mark the passage of time,[9][18] which is also portrayed by changing colour palettes.

[18][8] The score and setting convey David's emotional and mental fragility,[9][18] with a contrast drawn between the chaotic music and controlled cinematography.

[8] The episode's closing scene is, according to several critics, ambiguous, as it is unclear whether David has visited violence on Ted or on Sally.

[17][18][9] This mise-en-scène reflects "David's psychosis, and what he and Louise [have] lost in the death of Sally's twin brother".

[21][22] Dessau identified it as a "terrific instalment",[17] while O'Grady discussed it as a key example of how high-quality television continues to survive in the 21st century, as part of "a renaissance in British comedy".

[15] It was, for him, comparable with the best of Shearsmith and Pemberton's previous work;[19] Billen, similarly, characterised it as one of the best episodes of Inside No.

[16] For the freelance critic Dan Owen, "Diddle Diddle Dumpling" was a "characteristically rich and rewarding experience",[9] for Patrick Smith of The Daily Telegraph, it was a "delicious slice of macabre humour",[23] and for Hannah J Davies, of TheGuardian.com, it was "excellent", even if "not the strongest episode of the series".

[24] Mark Butler, of inews.co.uk, said that the episode "managed to weave a genuinely gripping and powerful half hour of TV from a seemingly bizarre and banal set-up: a testament to [Inside No.

[20] Also writing for The Times, Chris Bennion praised the "near genius" premise, calling the episode a "witty glimpse of midlife inadequacy" that became darker as it progressed.

[26] Butler identified the device of the shifting seasons as "a clever and striking touch", characterising the episode as moving from "laugh out loud" humour to "profoundly uncomfortable" interactions, with a "hard to swallow" and "disquieting" conclusion.