Clyde has developed a talent for art. Luke secretly entered one of his pieces in a contest, and it has won their class a trip to see the Mona Lisa, which is on display at a London gallery. But something hidden in the bowels of the gallery brings the painting to life, and Mona Lisa turns out to be a sinister woman gifted with unearthly powers. She forces the weak-willed curator, Lionel Harding, to help her search the gallery for her mysterious “brother”. And when Sarah Jane arrives to investigate, Mona Lisa traps her inside a painting -- leaving Luke, Clyde and Rani to stop the threat on their own.

One of two new writers recruited for the third season of The Sarah Jane Adventures was Brian Dooley. He was best known as the creator of the sitcom The Smoking Room, and he had contributed to the Doctor Who anthology Short Trips: Snapshots, published in 2007 by Big Finish Productions and edited by The Sarah Jane Adventures writer Joseph Lidster. The starting point for Dooley's script was the notion of artwork coming alive. When he began working on the storyline in November 2008, his adventure was intended to be made and broadcast third, and so Dooley was asked to limit Sarah Jane's involvement in order to give Elisabeth Sladen a mid-season break, akin to 2007's Whatever Happened To Sarah Jane? and 2008's The Mark Of The Berserker.

Dooley developed a serial which focussed on Leonardo da Vinci's famous portrait the Mona Lisa, painted in the early sixteenth century, which had also been key to the plot of the 1979 Doctor Who story City Of Death. Early drafts incorporated characters from other well-known works of art. They included the Lady of Shalott, a tragic Arthurian sorceress created by Alfred, Lord Tennyson in an 1833 poem and most famously depicted on canvas by John William Waterhouse in 1888; the Lady would take up arms as Mona Lisa's henchwoman.

Phil Ford undertook extensive rewrites of Brian Dooley's scripts in early 2009

When the intended season finale, The Wedding Of Sarah Jane Smith, was redeveloped as the year's third story in order to accommodate the availability of Tenth Doctor actor David Tennant, Dooley's adventure was shifted to the fifth spot in the schedule. Meanwhile, lead writer Phil Ford undertook extensive rewrites on Dooley's scripts during the early part of 2009. These revisions were so substantial that it was agreed that the finished episodes -- which gained the title Mona Lisa's Revenge -- should include an on-screen credit for Ford only.

Mona Lisa's Revenge was the third and final story of the year to be directed by Joss Agnew. Filming actually began during the production of his preceding serial, The Wedding Of Sarah Jane Smith. The only scene on Bannerman Road -- of Luke arriving home -- completed on May 21st, during work on Clinton Road in Penarth for the earlier adventure. Almost a month later, on June 19th, production resumed at the Barry Memorial Hall and Theatre in Barry for material set in the exhibition area of the International Gallery, where Clyde's winning artwork was displayed.

On June 22nd and 23rd, sequences outside the International Gallery and in various corridors were filmed at the Welsh National Museum in Cardiff; the location had previously been used to represent the same fictitious institution at the start of the 2009 Doctor Who Easter special Planet Of The Dead. On the first day at the National Museum, Agnew's team was joined by BBC News entertainment correspondent Lizo Mzimba, an ardent Doctor Who fan whose cameo appearance in Mona Lisa's Revenge was the fulfillment of a long-held ambition. Work on June 24th began at the show's regular studio facilities in Upper Boat, on the sets for Sarah Jane's attic and Luke's bedroom. Cast and crew then moved over to Hawthorn High School in Pontypridd to record the art class scenes. On the 25th and 26th, the Temple of Peace at the Welsh Centre of International Affairs in Cardiff offered a space suitable for the main gallery where the Mona Lisa hung.

June 29th was spent back at the Welsh National Museum and concentrated on exterior shots, as well as those in the lobby and on the main staircase. The basement area of the International Gallery, including the vault containing the Abomination, was actually located at Headlands School in Penarth; filming there spanned June 30th to July 2nd, with part of the last day reserved for some effects shots. July 6th saw Agnew's team return to the National Museum for one more day, with his itinerary including material in the shop, on the stairs, in the corridors, and outside the gallery.

• Doctor Who Magazine Special Edition #28, 13th July 2011, “Episodes 3.9/3.10: Mona Lisa's Revenge” by Andrew Pixley, Panini Publishing Ltd.