The single track Grain branch diverges away from the main line at Hoo Junction and crosses the Isle of Grain which is sometimes referred to as the Hoo Peninsula. The branch closed to passenger traffic in 1961 but remains open to this day as a freight only line.
At the far end of the line are several freight terminals including the London Thamesport container terminal, an aggregates terminal and an oil terminal handling imported aviation fuel.
There is also a short spur serving the Brett Aggregates terminal which handles sea-dredged sand and gravel from the Thames Estuary.
The Thamesport container terminal opened in 1990 with Freightliner services to the port commencing in January 1992. In 2010 construction of the new London Gateway Container port on the Essex bank of the River Thames began. The opening of this new facility marked the end of Freighliner trains to Thamesport with the final train running on the 6th November 2013.
In 1988 Foster Yeoman opened an aggregates terminal on the branch handling stone products imported by ship.
The site was involved with the construction of the Channel Tunnel including the manufacturing of the tunnel lining segments of the English side of the tunnel which were moved to the construction site at Folkestone by rail.
After the completion of the Channel Tunnel in 1994 the terminal continued to distribute aggregates by road, ship and rail and is a major supplier of ballast of the railways in the south east.
The branch became a mecca of Crompton fans in the mid 1990s as the Class 33s were in regular use working ballast trips along the branch. These trip workings between Hoo Junction and the stone terminal were then taken over by Class 37s in the early 00s.
Ownership of the terminal has now past to Aggregate Industries followings its purchase of the Foster Yeoman company in 2006 and still distributes stone products by rail to this day.
In 2018 a new flow of imported aviation fuel for Heathrow Airport began. These trains run to the Colnbrook oil terminal and were operated by Freightliner Heavy Haul. This flow was temporarily halted when long haul flights at the airport were dramatically reduced because of the pandemic.
GBRf have now taken over the operation of this flow with Class 66 number 66793 being a regular performer on this working.
Other freight flows along the branch have included bitumen and for a short period in the mid 90s imported coal. Test trains, weed killing trains, RHTT train and the occasional railtour have also visited the line over the years.