Question: Who owned the British train operating company that was the last operator of the London railway station which was replaced by the new Thameslink platforms at St Pancras in December 2007?

Context paragraphs:
Camden Town Hall: Camden Town Hall, known as St Pancras Town Hall until 1965, is the town hall for Camden London Borough Council.  It is located along Euston Road, opposite the main front of St Pancras railway station, with Judd Street to its rear.  It was constructed to a neoclassical design in 1934-7 for St Pancras Borough Council on the site of Georgian terraced housing.  It is a steel-framed building, clad with Portland stone.  The architect was A.J. Thomas, who also designed housing schemes for the borough.  It was extended in the 1970s.

St Pancras Basin: The St Pancras Basin, also known as St Pancras Yacht Basin, is part of the Regent's Canal in the London Borough of Camden, England, slightly to the west of St Pancras Lock.  Formerly known as the "Midland Railway Basin", the canal basin is owned by Canal & River Trust, and since 1958 has been home to the St Pancras Cruising Club.  The basin is affected by the large-scale developments in progress, related to King's Cross Central.

Midland Mainline: Midland Mainline was a train operating company in the United Kingdom owned by National Express that operated the Midland Main Line franchise from April 1996 until November 2007.  Midland Mainline ran fast and semi-fast passenger services from London to the East Midlands and Yorkshire, on the Midland Main Line.  Most services ran between London St Pancras and either Derby, Nottingham or Sheffield.  Some services extended to Burton upon Trent, Matlock, Barnsley, Leeds, York and Scarborough.

St Pancras Old Church: St Pancras Old Church is a Church of England parish church in Somers Town, central London.  It is dedicated to the Roman martyr Saint Pancras, and is believed by many to be one of the oldest sites of Christian worship in England.  The church is situated on Pancras Road in the London Borough of Camden, with the surrounding area and its international railway station taking its name.  St Pancras Old Church, which was largely rebuilt in the Victorian era, should not be confused with St Pancras New Church about a kilometre away, on the Euston Road.

Herne Hill railway station: Herne Hill railway station is in the London Borough of Lambeth, South London, England, on the boundary between London fare zones 2 and 3.  Train services are provided by Thameslink to London Blackfriars, Farringdon, St Pancras International and Luton Airport on the Thameslink route and by Southeastern to London Victoria (via Brixton) and Orpington on the Chatham Main Line.

Southeastern (train operating company): 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.

King's Cross Thameslink railway station: 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.

St Pancras New Church: St Pancras Church is a Greek Revival church in St Pancras, London, built in 1819–22 to the designs of William and Henry William Inwood.  It was historically often referred to as St Pancras New Church, in order to distinguish it from St Pancras Old Church, which stands some way to the north.

First Capital Connect: 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.

St. Pancras Renaissance London Hotel: The St. Pancras Renaissance London Hotel is a hotel in London, England, forming the frontispiece of St Pancras railway station.  It opened in 2011, and occupies much of the former Midland Grand Hotel designed by George Gilbert Scott which opened in 1873 and closed in 1935.  The building as a whole including the apartments is known as St Pancras Chambers and between 1935 and the 1980s was used as railway offices.  Its clock tower stands at 82m tall, with more than half its height usable.

Supporting paragraphs: King's Cross Thameslink railway station First Capital Connect
Answer: FirstGroup