Blon Fel - Fotch Passameer - Day Slitheen Blon Fel - Fotch Passameer - Day Slitheen was a female Raxacoricofallapatorian and a member of the criminal Slitheen family . On Earth , she took the skin of the human MI5 member Margaret Blaine . Regressed to an egg by the Heart of the TARDIS , she began a new life as Margaret Ag - Kris Therur - Ford Jingatheen . Biography . Upbringing . According to the story Blon told the Ninth Doctor , when she was thirteen she took part in her first hunt and knew that if she refused to join her family ' s criminal activities , she would undergo unpleasant ritual execution with Venom Grub s at the hands of her father . ( TV : " Boom Town " ) Criminal career . By March 2006 , the Slitheen family had killed Margaret Blaine so that Blon Fel - Fotch Passamer - Day could wear her skin . ( TV : " Aliens of London " ) The Ninth Doctor believed she had done it personally . ( TV : " Boom Town " ) She went along with her family ' s plan to trigger a nuclear war on Earth , in order to devastate the planet and sell the radioactive remains as starship fuel . ( TV : " World War Three " ) She was present at 10 Downing Street with her fellow Slitheen , " Joseph Green " and " Oliver Charles " . Green had taken over the government as Acting Prime Minister , which would give the Slitheen more power in Britain . Blaine was present when the Slitheen murdered General R . Asquith , and remained with Green for the rest of the crisis . When Rose Tyler , Harriet Jones and Indra Ganesh discovered the body of the Prime Minister , Blon taunted them and started to kill Indra . ( TV : " Aliens of London " ) Blon hunted down Rose and Harriet , but was distracted by the Doctor when he entered with a fire extinguisher . The Doctor , Rose and Harriet placed themselves safely behind the walls of the Cabinet Room . Thinking they couldn ' t do anything trapped inside the " box " , Blon continued with the plot . She took the skins of fellow Slitheen members who had been summoned to Downing Street and waited for the launch codes to be given to Downing Street . The Doctor contacted Mickey Smith , who launched the missile UGM - 84A at Downing Street , killing the Slitheen while the Doctor , Rose and Harriet rode out the explosion inside a small , sturdy cupboard . ( TV : " World War Three " ) Blon escaped the destruction of Downing Street by using an emergency teleport which could only carry one . The teleport landed her in a skip on the Isle of Dogs before arriving in Cardiff , where she managed to get herself elected Lord Mayor of Cardiff . ( TV : " Boom Town " ) Her predecessor , Barry Jackson , had killed the former mayor and blamed it on the Auton invasion . ( AUDIO : " One Rule " ) Secretly , Blon planned to take advantage of the space - time rift located there and advocated a plan for a proposed nuclear power plant called Blaidd Drwg . She wanted to cause an " accident " at Blaidd Drwg . This disaster , located so near the rift , would destroy Earth and provide her tribophysical waveform macro - kinetic extrapolator with sufficient power for her to ride the " surf " into space to escape . She knew that failing this , anyone who arrested her would take the extrapolator for themselves , having " considerable technology of their own " and being " captivated " by the extrapolator . The extrapolator was programmed to lock onto the nearest alien power source and open the rift , still allowing her escape . She killed anyone who questioned her plans , such as Mr Cleaver . However , in a rare act of mercy , she spared the journalist Cathy Salt after hearing the young woman talk about her family , reminding Blon of her own lost relatives . Soon after , the Ninth Doctor and his companions arrived to stop her ; Jack Harkness confiscated the extrapolator and used it to refuel the TARDIS quicker . The Doctor remained uncertain as to what do as she had been sentenced to death on her homeworld in absentia ; Blon pleaded the Doctor for mercy and clemency . When the extrapolator began opening the rift through the TARDIS , Blon , threatening Rose , demanded Jack to place the extrapolator at her feet . The extrapolator nearly pulled apart the TARDIS , but the heart of the TARDIS was forced open and Blon looked directly into its light ; she was regressed backwards along her timeline to the form of an egg . The Doctor returned her to her home planet to be placed with another family . ( TV : " Boom Town " ) Second chance . Renamed Margaret , the former Slitheen was adopted by the Jingatheen family . Left with her human skin suit , Margaret would keep and wear it throughout her life . Eventually , she joined the Shadow Proclamation , under which she worked as a Detective Inspector . Attached to the Judoon rocket " Typho " , Margaret boarded the Max Capricorn container ship " Jeden " with the Judoon led by Captain Nibri and came face to face with the Twelfth Doctor . ( COMIC : " A Confusion of Angels " ) Personality . As Blon Fel - Fotch Passameer - Day Slitheen . Having been brought up in a criminal family , Blon was fixated on making a profit whatever the cost , going as far as to commit murder . She lacked any form of empathy or morals , and was more than willing to commit terrible actions such as murder in order to further her or her family ’ s goals . Blon held particular disdain towards humans , comparing wiping out mankind to “ stepping on an ant hill ” . She described Earth as a savage and ” godforsaken rock ” . ( TV : " World War Three " ) Despite her brutality and killer instinct , Blon proved to be intelligent , calculating , patient and manipulative during her reign as Mayor of Cardiff , having set up a plan to destroy Earth as well as maintaining contingencies . ( TV : " Boom Town " ) However , Blon was capable of rare acts of mercy . But the Doctor simply reduced this to being how Blon lived with herself being a killer , which she reluctantly acknowledged . As Margaret Ag - Kris Therur - Ford Jingatheen . After having been given a second chance at life , Blon , renamed Margaret , was raised by the Jingatheen family and grew up to become an agent of the Shadow Proclamation . Once she met the Doctor again , she showed courage , bravery and dedication , standing by the Doctor and defending his allies against the Weeping Angels . ( COMIC : " A Confusion of Angels " Other information . While she served as mayor of Cardiff , Idris Hopper served as her secretary . ( TV : " Boom Town " , PROSE : " The Twilight Streets " )