From the Wikipedia page [1]
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. The development will facilitate cross-London journeys, which means that passengers will no longer have to change trains in London. Work includes platform lengthening, station remodelling, new railway infrastructure, and new 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, initially expected to be complete in December 2019, now has an uncertain date of completion. The Thameslink Programme is being carried out by Network Rail in association with the relevant train operating companies.
The website is [2]