When the London and South Western Railway Company took over the Devon and Cornwall Railway Company, it agreed to respect the undertakings given by that Company, one of which was to improve to foreshore near the Devonport terminus.   Indeed, the Lord of the Manor of Stoke Damerel, Sir John Saint Aubyn, had given the Company the land upon which the Station was built on the condition that a line be run down to the foreshore.  The Stonehouse Pool Improvement Act received the Royal Assent on July 13th 1876.

Preliminary work was already under way in January 1878 and at the beginning of October 1878 the line was reported as being ready for use in about three weeks time.

The branch commenced at the five-arch road bridge just to the east of Devonport Station and then ran into a cutting and then a tunnel beneath the goods shed.  Provision had already been made for this when the Station was erected.  Emerging from the tunnel, the line then crossed the road leading to the old rectory house and ran beside the road on a rubble embankment.  The line gradually fell to the point where it ran underneath the main Stonehouse to Devonport road on the Devonport side of Stonehouse Bridge.  It terminated a few yards beyond that point, in a 20-feet deep cutting beneath the Bluff Battery.

Mr Brady, of Barnstaple, north Devon, was the contractor.  The tunnel under Devonport Hill/Stonehouse Hill was constructed without interruption to the vast amount of traffic using that road, including the trams.  Stone from the cutting was used in the construction of the bridge.

It was then up to the Stonehouse Pool Improvement Company to arrange the construction of the lines on the foreshore for the benefit of unloading vessels at the quayside.

The London and South Western Railway Company was quick to realize that this Branch could be adapted for ocean liner passenger traffic, in competition with the Great Western Docks at Millbay.   This they did and commenced renting the line on the quayside from the Improvement Company on Friday December 25th 1885.  The Board of Trade's Inspector approved the use of the line for passenger traffic around the same time.

It was announced on Monday February 15th 1886 that: 'The Devonport New Quays and London & South Western Railway Station, Stonehouse Pool' were now open for traffic.  The Quays had a depth of water at ordinary low spring tides of 18 feet, although this went to 60 feet a few feet out.  There was, of course, a long list of landing rates, ranging from 6d for a hundred deals, or for bulls, cows and horses, down to ½d for a hogshead of beer or cider, or for a quarter of wheat, malt or barley.  Foreign vessels lying at the Quays had to pay 4d per registered ton.

Williams states that the line opened for goods traffic on March 1st 1886.  Given the announcement referred to above, placing the opening in mid-February, this may have been the date upon which the first traffic was recorded.  It also suggests that although the line was ready in 1878 it may not have carried any traffic until the completion of the New Quays in 1886.

During 1903 and 1904 the London and South Western Railway erected a passenger station to cater for transatlantic liner traffic.  The Ocean Quay Station was opened on Saturday April 9th 1904, when the American Line's "Saint Louis" became the first to call and the inaugural Ocean Special was run to London Waterloo Station.

Early on the morning of Sunday July 1st 1906, one of its 'ocean specials' was speeding so fast through Salisbury Station that it reeled on the curve in the Station and collided with a train of empty milk trucks.   Of the 43 passengers on board 24 were killed.  The LSWR ceased to use the Stonehouse Pool for passenger traffic from May 28th 1910.

A return submitted on November 17th 1927 to the Southern Railway Company by the station master at Devonport indicated that the signalling was removed at the time of closure to passenger traffic.  By 1927 the station buildings were being used for general storage and other buildings were being let for the curing and packing of herrings.   The station master reckoned that about forty wagons could be held at the quayside; any more would have been impracticable.

Freight traffic continued and Stonehouse Pool Signal Box at the level crossing over Richmond Walk was still manned until Wednesday February 1st 1928.

From March 25th 1934 until further notice the special instruction for working this branch were as follows:

This line, which is worked as a siding, connects with Devonport goods yard by means of hand points which lie normally for the goods yard.  These points must be secured by padlock when not in use, and the key kept in the signal box at Devonport.

A Shunter, or Shunters, as necessary, must accompany all trains passing over the line, and the Enginemen and Shunters must exercise extreme care when working on the branch to ensure that the line or sidings over which they require to pass are clear for their use.

The gates at Richmond Walk level crossing are maintained normally across the railway, secured in this position by hand bolts and padlocks, and trains proceeding from Devonport to Stonehouse Pool must be brought to a stand well clear of the level crossing gates and the brakes applied.

The man in charge of the movement must then unlock the gates and place them across the roadway for the engine or train to pass on to the quay lines.

When the train has passed on to the Stonehouse Pool quay lines, clear of the level crossing, the gates must be again opened to the public and secured and padlocked in this position.

When the work at Stonehouse Pool has been completed, and the train is ready to leave for Devonport, the man in charge must again place the crossing gates across the roadway, after which the train should be drawn forward clear of the crossing on the Devonport side, where it must be brought to a stand, and the brakes applied.

The man in charge of the operation must then advise the Signalman at Devonport by means of the telephone which is provided at the crossing, that the train is ready to leave, and after having obtained the Signalman's permission for the departure of the train for Devonport he must replace the crossing gates across the railway, re-lock them in position, and proceed with the train to Devonport.

Certain types of engine cannot be passed safely over the quay lines at Stonehouse Pool, and the staff must ascertain before leaving Devonport to what extent the engine in their charge may be used on the quay.

"N" and "N 1" class engines may be permitted to work over the Stonehouse Pool line as between Devonport station and a point 100 yards on the wharf side of Richmond Walk level crossing, at which notice boards are fixed.

The load of a goods train from Stonehouse Pool to Devonport, hauled by one engine, must not exceed equal to 12 loaded goods wagons with one brake van at the rear, in which a man must ride.

A 3-ton crane, purchased in 1926, was provided at Stonehouse Pool, with a maximum lift of 20 foot.

The station buildings were completely destroyed during the Second World War, when the manager of Messrs J Lyons & Company's store was killed while fire watching.

With the Ocean Quay Station buildings having been closed since 1910 and destroyed during the Second World War, the line's fortunes steadily declined and in 1966 the branch carried its last revenue earning traffic.  Official closure is said to have been on Saturday May 30th 1970.