Dover to Boulogne and Calais routes Seaspeed investigated various options for its intended services, intensifying its evaluation efforts in 1967.
Dover,
Folkestone and
Pegwell Bay were considered as well as
Lydd-on-Sea,
Brighton,
Le Touquet and the
Isle of Man. However, management was keen to align with existing
Sealink services (also owned by British Rail) so that, in the event of a vessel's failure (or bad weather conditions), it could be more readily substituted for. Thus, either Dover or Folkestone on the English side and
Calais or
Boulogne-sur-Mer on the French side became the preferred options. Folkestone was eliminated due to its small harbour, unable to cater for large hovercraft, and high exposure to southerly winds. SNCF, being keen to support the initiative, offered to build a railway line and station adjacent to the proposed Boulogne hoverport at its own expense. In August 1968, Seaspeed commenced its cross-Channel services from the Eastern Docks at Dover, England to Boulogne-sur-Mer, France using its first SR.N4
The Princess Margaret. In 1970, Dover to Calais was added with
The Princess Anne respectively. Seaspeed also operated a single French-built
SEDAM N500 hovercraft, designated
N500-02,
Ingénieur Jean Bertin, from summer 1977. In concept, it looked to be a capable vehicle, possessing advantages over the SR.N4 such as storing cars over two decks rather than one. Despite this, the N500 was beset by design and operational problems that would never be successfully resolved; following a somewhat sporadic service on the cross-Channel route, the N500 was permanently withdrawn during 1983 and later scrapped.
Competition with Hoverlloyd Seaspeed was not the only hovercraft operator that decided to move on the cross-Channel market at the time; a rival company,
Hoverlloyd, was also established in the 1960s and launched its own competing route between Calais and
Ramsgate. The two firms would compete with one another, as well as incumbent ferry operators, for market share throughout Seaspeed's existence. Despite this rivalry, considerations were made towards mutually beneficial cooperation; at an early stage, Seaspeed's management considered conducting SR.N5 services out of Hoverlloyd's hoverport at Ramsgate.
Increased reliability but poor profitability The cancellation rate for engineering reasons fell from almost 30% in 1968 to less than 5% in 1973. However, unlike Hoverlloyd, except in 1973 and 1976 when Seaspeed returned a profit of £100,000 and £5,000 respectively, the company made a loss before interest in every year since 1968. These drastically increased towards the end of the decade with British Rail continuing to guarantee operations. Seaspeed recorded a pre-tax loss of -£599,000 in 1977 and -£2,234,000 in 1978, then -£2,900,000 in 1980 and -£1,423,000 in 1981 when the company ceased trading and merged with Hoverlloyd. According to a parliamentary paper, over the period 1973 to 1980, Seaspeed incurred a net operating loss of £7 million. If interest had been charged at commercial rates on the balance outstanding to British Rail, there would have been not only a loss over the period, but, moreover, in each individual year, and the company would have been insolvent without the guarantee from British Rail.
Coach services Similar to Hoverlloyd's provision, Seaspeed operated a coach link between Calais and Brussels which, in 1980, conveyed 20,000 passengers.
SR.N4 modifications In early 1976, the British Rail board approved a plan to drastically upgrade the two SR.N4s by lengthening them, achieved via the insertion of an almost 17.1 metre (56.1 ft) long section. This change increased the passenger capacity of the craft from 254 to 418, while also raising the car capacity to 60. According to Paine and Syms, rival operator Hoverlloyd was interested in the modification, but did not have such work done to their own SR.N4 fleet, reportedly due to a lack of available finances. ==Isle of Wight services==