The South Eastern Railway (SER) first reached Tonbridge (then known as "Tunbridge") in May 1842. The site of the original station was on the east side of the road bridge over the railway, opposite its current location to the west of the bridge. The building of the station obliterated the last remains of Tonbridge Priory. At the time, the line ran to London Bridge via Redhill and Croydon, using the Brighton Main Line. It served as a temporary terminus until December 1842, when the line reached Ashford. A couple of years later the through line to Dover opened. A small engine shed was built; the date of opening is uncertain but it is presumed to date from the opening of the line. On 20 September 1845, a branch to opened. The station was later renamed "Tunbridge Junction". Over the next seven years the branch was extended to Hastings. Access to the line to Hastings was via an indirect link which required a reverse. This arrangement lasted until 1857 when a steeply climbing direct route was opened.