Editing SR.N4 (section)

==Operational service==
[[File:Hovercraft in Dover.jpg|thumb|''Princess Margaret'' at the mouth of the [[Port of Dover|Western Docks in Dover]], 1998]]

Upon completion of the prototype SR.N4, Charles Anthony Brindle, the Managing Director of British Rail Hovercraft, was responsible for establishing the first cross-Channel route for scheduled services by the type.<ref>{{cite web |url=http://www.nrm.org.uk/railwaystories/railwayvoices/charlesanthonybrindle |title=Charles Anthony Brindle |publisher=[[National Railway Museum]] |location=UK |archive-url=https://web.archive.org/web/20160718010656/http://www.nrm.org.uk/railwaystories/railwayvoices/charlesanthonybrindle |archive-date=2016-07-18}}</ref> In October 1966, Brindle and several engineers surveyed several potential sites on both the British and French sides of the English Channel using an [[SR.N6]] to determine their suitability for the hovercraft service, which had been given the name [[Seaspeed]]. Amongst the most suitable candidates had been [[Port of Dover|Dover]] or [[Folkestone Harbour|Folkestone]] on the English side and [[Port of Calais|Calais]] or [[Boulogne-sur-Mer|Boulogne]] on the French side.{{sfn|Paine|Syms|2012|p=230}}{{sfn|Paine|Syms|2012|p=234}}

It was soon determined that Dover and Boulogne would be the preferable option for the maiden route, a decision that had been motivated in part by the local [[Chamber of Commerce]] having agreed to build a suitable hoverport to readily facilitate such operations.{{sfn|Paine|Syms|2012|p=230–234}} As there was no funding available for pre-service passenger trials, the opening season of active operations effectively served as a continuation of the trials activities as well. Brindle was aware that BHC would not be paid until the SR.N4 was in service, and thus there was a considerable emphasis placed on getting the craft ready for commercial use right at the point of delivery.{{sfn|Paine|Syms|2012|p=309–310}}

In August 1968, the first SR.N4 entered commercial service with the GH-2006 ''Princess Margaret'' being initially operated by Seaspeed between Dover and Boulogne.{{cn|date=July 2024}} Rival operator [[Hoverlloyd]] built the world's first purpose-built hoverport at [[Ramsgate Hoverport]], specifically designed for the SR.N4, to also serve the Calais route.{{cn|date=July 2024}}

The journey time from Dover to Boulogne was roughly 35 minutes, with six trips per day being conducted at peak times. The fastest ever crossing of the English Channel by a commercial car-carrying hovercraft was 22 minutes, achieved on 14 September 1995 by the SR.N4 Mk.III GH-2007 ''Princess Anne'' on its 10:00&nbsp;a.m. service.<ref>{{cite news |url=http://news.bbc.co.uk/onthisday/hi/dates/stories/june/15/newsid_3025000/3025267.stm |title=Hovercraft Facts |work=1966: Hovercraft deal opens show |publisher=[[BBC News]] |date=15 June 1966 |accessdate=9 April 2010}}</ref><ref>{{cite web |url= http://www.dover-kent.co.uk/transport/hovercraft.htm |title= Hovercraft |access-date= 2008-01-23 |work= Dover – Lock and Key of the Kingdom |publisher= www.dover-kent.co.uk |url-status= dead |archive-url= https://web.archive.org/web/20120917130412/http://www.dover-kent.co.uk/transport/hovercraft.htm |archive-date= 17 September 2012 |df= dmy-all }}</ref>

[[File:SRN4Loading89.jpg|left|thumb|''Princess Anne'' loading in 1989]]

In 1972, the first SR.N4s were temporarily withdrawn for conversion to Mk.II specification which would provide for seven further car spaces and 28 more passengers. The first of the enlarged craft, the ''Swift'', entered service at the beginning of February 1973.<ref name=Autocar197302>{{cite magazine| title =Hovering along on the Crest of a Wave |magazine=[[Autocar (magazine)|Autocar]] |page=6 |date = 8 February 1973}}</ref> The capacity increase was achieved by removing an inner passenger cabin in order to accommodate the extra cars and widening the outer passenger cabin: this was achieved without changing the overall footprint of the craft.<ref name=Autocar197302/> New aircraft-style forward-facing seats created an atmosphere of enhanced sophistication, and a redesigned skirt was intended to reduce window spray, enhancing the view out for passengers, and to give a smoother ride in rough seas: contemporary reports nevertheless commented on the "unsprung" nature of the ride.<ref name=Autocar197302/>

After 1976, a pair of SR.N4s were refitted with new deep skirts and stretched by almost {{convert|56.1|ft|m|1|abbr=on}}, increasing capacity to 418 passengers and 60 cars at the cost of a weight increase to roughly {{convert|320|t|LT|0|abbr=on}}.{{sfn|Paine|Syms|2012|p=595}} To maintain speed, the engines were upgraded to four {{convert|3800|shp|kW|0|lk=in}} models, which were fitted with four {{convert|21|ft|m|1|abbr=on|adj=on}} diameter steerable [[Dowty Rotol]] [[Propeller (aircraft)|propeller]]s. The work cost around £5 million for each craft, and they were designated Mark IIIs; the improvements allowed them to operate in seas up to {{convert|11|ft|6|in|m|1|abbr=on}} high and with {{convert|57.5|mph|km/h|1|adj=on}} winds.{{sfn|Paine|Syms|2012|p=595–596}}

The two main commercial operators (Hoverlloyd and Seaspeed) merged in 1981 to form [[Hoverspeed]], which operated six SR.N4 of all marks.<ref>{{cite news |first=Justin |last=Parkinson |url=https://www.bbc.com/news/magazine-34658386 |title=What happened to passenger hovercraft? |work=BBC News Magazine |location=UK |date=9 November 2015 |access-date=2023-06-18}}</ref> The last of the craft was withdrawn from service in October 2000 and Hoverspeed itself ceased operations in November 2005.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/uk_news/england/kent/4406224.stm |title=Many jobs lost as ferries stop |work=BBC News |date=4 November 2005 |access-date=2023-06-18}}</ref>

=== Accidents ===
Most incidents were benign and resulted in little more than the vehicles towed back to shore.  In 1978, the GH-2007 ''Princess Anne'' lost much of her air-cushion skirt in heavy seas 7 miles off Dover, resulting in a [[Marine_Accident_Investigation_Branch|MAIB]] investigation.{{sfn|Investigation of Heavy Weather Damage}} However, in March 1985, 4 passengers lost their lives when GH-2006 ''Princess Margaret'' crashed into a pier at the entrance of [[Port of Dover|Dover Harbour]] from Calais in force 6 to 7 heavy seas.<ref>{{Cite book|last=Hollebone|first=Ashley|title=The Hovercraft: A History|publisher=History Press|year=2012|isbn=9780752490519|page=26}}</ref><ref>{{cite web |url=https://discovery.nationalarchives.gov.uk/details/record?catid=8419462&catln=6 |title=Report of the inquiry into the accident to hovercraft 'The Princess Margaret' |work=National Archive |location=UK}}</ref>

===Military interest===
The [[Royal Navy]] considered a [[mine sweeping]] version of the SR.N4, hovercraft being almost invulnerable to [[Naval mine|mines]]. A minesweeping version of the SR.N4 was thought to be capable of carrying the same equipment as a [[Hunt-class mine countermeasures vessel]], while being cheaper to purchase, although more expensive to operate. The use of hovercraft for minesweeping never got further than the concept stage, although an [[SR.N3]] was used by the Inter-Service Hovercraft Unit for trials.{{sfn|Brown|Moore|2012|p=140–141}}