Set in Northumbria in 1066, before the Battle of Stamford Bridge, the serial features the time traveller the First Doctor (William Hartnell) and his companions Vicki (Maureen O'Brien) and Steven Taylor (Peter Purves) as they attempt to outwit the time traveller the Monk (Peter Butterworth), who is plotting to change the course of European history by wiping out King Harald Hardrada's Viking invasion fleet, leaving Harold Godwinson and the Saxon soldiers fresh to defeat William of Normandy and the Norman soldiers at the Battle of Hastings.

Spooner, who was leaving his role as story editor before this serial, was commissioned to write The Time Meddler by producer Verity Lambert.

The Time Meddler was the first serial under new story editor Donald Tosh, and the crew was joined during production by John Wiles, who was soon to replace Lambert as producer.

The Time Meddler received a smaller audience than The Chase, with an average of 8.42 million viewers across the four episodes; the Appreciation Index also saw a drop.

The First Doctor (William Hartnell) and Vicki (Maureen O'Brien) find Steven Taylor (Peter Purves) aboard the TARDIS after he stumbled in during a disoriented state on Mechanus.

He tries to persuade the villagers to light beacon fires on the cliff tops, secretly wishing to lure the Viking fleet to land; Wulnoth tells the Monk that he agrees, but admits to Edith that he suspects danger.

Ulf and Sven form an alliance with the Monk and tie up the Doctor's party while the three of them take the neutron bomb shells to the cannon on the beach.

[10] The Time Meddler was the first serial under new story editor Donald Tosh, having been offered to work on either 199 Park Lane or Doctor Who after the cancellation of Compact.

[8] Douglas Camfield was assigned as director in April, having recently finished work on The Crusade (1965); he was pleased with Spooner's scripts, finding them among his best.

[4][a] Set designer Barry Newbery constructed the Saxon's hut in the style of a cruck, painting the studio floor black to resemble ox blood.

He envisaged the characters as a schoolboy prankster from the Billy Bunter books;[11] in the script, he was described as "mischievous, sly and cunning ... with a 'naughty boy' look".

[23] Recording on the serial was due to take place at Riverside Studios until late May, when it was decided to switch back to Television Centre.

Hartnell found the change unsettling and threw fake tantrums to scare the production team to obey him; he later admitted to other cast members that he was only joking.

[28] The first episode was broadcast later than usual—6:55 p.m. instead of 5:40 p.m.[28]—due to an extended edition of the preceding program Grandstand covering the Henley Regatta and Wimbledon Championships final.

[28] A twelve-second clip from the fourth episode remained missing from the complete prints of the serial, as it was removed by censors; it depicted a scene where Vikings are stabbed to death.

Roberts used complete 16mm prints of the first and third episodes being held by a private collector to restore most of the cuts; they were transferred to digital D3 tape on 20 December 1991.

Television Today's Bill Edmund enjoyed the character of the Monk and Butterworth's performance, but was disappointed by the lack of monsters in the serial.

[29] In a review for the BBC series Hereward the Wake, The Observer's Maurice Richardson found it difficult to "suspend disbelief" for the show's time setting after watching Doctor Who's "remarkable essay in this period".

In The Discontinuity Guide (1995), Paul Cornell, Martin Day, and Keith Topping described the serial as "an atmospheric story" and praised the performances, particularly that of Hartnell and Butterworth.

[2] In The Television Companion (1998), David J. Howe and Stephen James Walker lauded Butterworth's "deft, understated performance", especially in his scenes with the Doctor, and applauded Camfield's direction as "very polished and features some nice touches", though they felt that the conclusion was simple and that the Vikings and Saxons "are sketched in merely as caricatures".

[34] In 2008, Den of Geek's Simon Brew praised Butterworth's performance, noting that the serial "really hits its stride" with the sparring between the Doctor and the Monk, but felt that the story was not enough to cover four episodes.

[36] IGN's Arnold T. Blumberg highlighted the chemistry between Hartnell and Butterworth, the competency of Vicki and Steven, and the visual atmosphere, but felt that the plot contained some clichés.

[3] In 2009, Patrick Mulkern of Radio Times called the serial "an utter delight" and "the Doctor Who equivalent of comfort food", praising Butterworth's performance and Camfield's direction.

Club's Christopher Bahn enjoyed the Monk and the introduction of Steven, and lauded the pacing of Spooner's script and Camfield's direction.

[35] Selected stock music from the serial was included in Space Adventures, a cassette soundtrack compiled by Julian Knott and published by DWAS Reference Department in September 1987, limited to 300 copies; it was expanded and re-issued as a CD in October 1998.

[42][43] The story was revisited as part of the spin-off series Tales of the TARDIS, released on BBC iPlayer on 1 November 2023, with new scenes starring O'Brien and Purves.