Southern is the brand name used by the Govia Thameslink Railway (GTR) train operating company on the Southern routes of the Thameslink, Southern and Great Northern franchise in England.
 It is a subsidiary of Govia, a joint venture between transport groups Go-Ahead and Keolis, and has operated the South Central rail franchise since August 2001 and the Gatwick Express service since June 2008.
 In July 2015, the franchisee was subsumed into GTR, but the Southern and Gatwick Express brand identities were retained alongside those of Thameslink and Great Northern.
The Thameslink Programme, originally Thameslink 2000, is a £6 billion project in south-east England to upgrade and expand the Thameslink rail network to provide new and longer trains between a wider range of stations to the north and to the south of London without requiring passengers to change trains in London.
 Work includes platform lengthening, station remodelling, new railway infrastructure, and additional rolling stock.
 The project was originally proposed in 1991 following the successful introduction of the initial Thameslink service in 1988.
 After many delays, planning permission was granted in 2006 and funding was approved in October 2007.
 Work started in 2009 and is expected to be complete in 2018.
 The Thameslink Programme is being carried out by Network Rail in association with the relevant train operating companies.
Govia Thameslink Railway (GTR) is a train operating company that operates the Thameslink, Southern and Great Northern (TSGN) rail franchise in England.
 Within the franchise, GTR runs the Thameslink, Great Northern, Southern and Gatwick Express airport services.
London & South Eastern Railway Limited, trading as Southeastern, is a British train operating company in South East England.
 It is the key operator for commuter and regional services in South East London and Kent but also serves parts of East Sussex.
 Southeastern trains operate along three main routes: the Southeastern Main Line from London Cannon Street and London Charing Cross to Dover via Sevenoaks; the Chatham Main Line between London Victoria and Dover/Ramsgate via the Medway towns; and High Speed 1 from London St. Pancras.
 On 1 April 2006 it became the franchisee for the new Integrated Kent franchise (IKF), replacing the publicly owned South Eastern Trains on the former South Eastern franchise.
First Capital Connect (FCC) was a British train operating company, owned by FirstGroup, that operated the Thameslink Great Northern franchise from April 2006 to September 2014.
Northern Rail was an English train operating company owned by Serco-Abellio that operated the Northern franchise from 2004 until 2016.
 It was the primary train operator in Northern England, and operated the most stations of any train operating company in the United Kingdom.
 Northern Rail was replaced on 1 April 2016 by Northern.
Gatwick Express is a high-frequency rail passenger service between London Victoria, Gatwick Airport, and Brighton in South East England.
 It is the brand name used by the Govia Thameslink Railway train operating company on the Gatwick Express route of the Thameslink, Southern and Great Northern franchise.
King's Cross Thameslink station is a closed railway station in central London, England.
 It served the Thameslink route but was replaced by new Thameslink platforms at St Pancras in December 2007.
 The last operator of the station was First Capital Connect.
 The site is on Pentonville Road, about 160 yd from King's Cross station.
Thameslink and Great Northern are the brand names used by the Govia Thameslink Railway train operating company on the Thameslink and Great Northern routes of the Thameslink, Southern and Great Northern franchise, previously operated by First Capital Connect.
Go-Op (full name Go!
 Cooperative Ltd), is an open access train operating company which is currently proposing to operate a service between Taunton and Swindon, via Westbury.
 It aims to become the first cooperatively owned train operating company in the United Kingdom, to improve access to the public transport infrastructure through open access rail services linking main lines to smaller market towns, and co-ordinating services with light rail and bus links and car pools.
 Go-Op intended to begin operating rail services in the spring of 2014, however difficulties in obtaining rolling stock and severe financial difficulties incurred by their main partner The Co-operative Bank have delayed these plans.

Question: What are the operating years of this British train operating company that was the last operator of King's Cross Thameslink railway station?
Answer: April 2006 to September 2014