Home - Army Fifth Operational Corps The Home - Army Fifth Operational Corps — or the Fifth Operational Corps for short — was a military organisation which defended the Earth from alien threats in the late 20th century . The organisation ' s acronym represented the word ' Fifth ' with the Roman numeral ' V ' , spelling HAVOC . ( PROSE : " The Enfolded Time " ) While primarily British Army , they also drew officers from the Royal Air Force and Royal Navy . ( PROSE : " The Grandfather Infestation " ) The organisation was a successor to the previous four Operational Corps , ( PROSE : " Mutually Assured Domination " ) LONGBOW , ( PROSE : " Moon Blink " ) and ICMG ( PROSE : " The Dogs of War " ) and a precursor to UNIT . ( PROSE : " The Enfolded Time " ) Ian Gilmore called the classified Home - Army Operational Corps as " the UK ' s best kept secret " , due to their wide - ranging executive powers : while he didn ' t want to say they acted above the law , he said Winston Churchill had " made a lot of , shall we say , " progressive " use of them . " ( PROSE : " The Dogs of War " ) Organisation . Senior staff and communications & monitoring were located at Dolerite Base , under Edinburgh Castle . 1st Battalion were stationed at Stirling Castle , Scotland , while 2nd Battalion had no permanent base so they could be a more mobile response unit . A mobile HQ was set up in a Hercules transport plane . ( PROSE : " The Grandfather Infestation " ) Officers were trained at the . ( PROSE : " The Cult of the Grinning Man " , " The Grandfather Infestation " ) History . After ICMG was destroyed in 1966 , several important people in the British government wanted to create another alien defence organisation to replace it . ( PROSE : " The Dogs of War " ) The numerous alien attacks in early 1969 gave Major General Oliver Hamilton and Ian Gilmore the leverage needed to convince the government to create the Fifth Operational Corps . ( PROSE : " Mutually Assured Domination " ) It was funded in large by industrialist Peyton Bryden , who wished to benefit from the advanced alien tech so that Bryden Industries could continue to compete against International Electromatics , so its budget would be ' off the books ' . To further keep the group secret , the initial soldiers were often the rotten apples of other regiments so nobody would wonder where they were going . The MOD liaison to the Corps was Peter Grant , who had a niece that was into ' spy stuff ' . The HQ of the Corps was located in Dolerite Base with their troops stationed at Stirling Castle and in Imber . Alien technology was confiscated from the Vault and moved to Dolerite . ( PROSE : " Moon Blink " , " The Showstoppers " , " The Grandfather Infestation " ) The Fifth was initially commanded by Colonel Alistair Lethbridge - Stewart , who promoted to brigadier shortly before officially taking command of Dolerite Base in Edinburgh . The Head of Science & Research was Doctor Anne Travers . ( PROSE : " The Showstoppers " ) In 1973 , Lethbridge - Stewart left the Fifth Operational Corps to create UNIT . He was ordered to pretend that Corps had never existed . ( PROSE : " The Enfolded Time " ) The Corps continued , working on some of UNIT ' s more secretive operations . After Lethbridge - Stewart took over UNIT UK , Walter Douglas was promoted to brigadier and resumed command . ( PROSE : " Ashes of the Inferno " ) It continued to secretly protect the UK in 1990 but had now dropped the " Home Army " label . William Bishop was now second - in - command . ( PROSE : " The Enfolded Time " )