The navigator of a racing yacht which was in collision with an oil tanker has described the ''rabbit in the headlights'' moment when he realised the impact was imminent.

Southampton Magistrates' Court has heard how the Atalanta of Chester was involved in the accident with the 260-metre Hanne Knutsen on the first day of Cowes Week in August 2011.

The yacht's skipper, Roland Wilson, a lieutenant in the Royal Navy Reserves, is alleged to have been negligent and faces three charges of contravening maritime regulations.

Footage of the incident, in which one crew member suffered head injuries and another abandoned ship, has been posted on YouTube.

The court has heard that the Atalanta sailed ''perilously'' close to the 120,000-ton vessel despite Mr Wilson seeing it from five miles away.

Michael Shrives, a retired Navy commander who has 41 years experience of sailing at Cowes Week and who is general secretary of the RN Sailing Association, told the court the collision came after the yacht came to a sudden stop after losing the wind.

Mr Shrives, who was navigating the Atalanta, said he expected to pass port-to-port with the Hanne Knutsen as it had given a short blast of its horn indicating it would turn to the starboard, a turn he said it did not make.

The trial has heard the tanker changed course to avoid a stranded motor vessel, the Joy C.

He said the seriousness of the situation became apparent when the Atalanta lost the wind and Wilson went to turn the engines on to motor out of the way.

Mr Shrives said: ''It was almost like rabbits in the headlights at that stage, it was too late to do anything.''

He continued: ''There was a false expectation that the tanker would take a track that it subsequently didn't as we have seen these big ships coming through that area.

''We thought the Hanne Knutsen would follow the patrol boat and would pass a good distance port- to-port and the danger would be through and we would be passing it on our way to our mark.''

Simon Lusty, marine officer on the pilot boat Spitfire, which was assisting the Hanne Knutsen with its arrival at Fawley oil refinery, said the Atalanta was spotted ahead of the tanker and the Spitfire approached it to warn the crew.

He said: ''I told the skipper at the helm that he needed to start his engines and clear the area, there's a tanker coming down.

''I cannot say it was the helmsman but I had acknowledgement from someone in the cockpit.''

Mr Lusty described how he was then alerted to the Joy C, which was in difficulties after its engines failed close to the Hanne Knutsen.

He said: ''The skipper was waving his hands in some kind of distress and was unable to clear the area.

''We left the yacht (Atalanta) alone having given it the instructions, happy it would be adhered to. By the time we got back to the Joy C it was a bit hectic and Joy C was too close to the Hanne for us to intervene, to get in-between, to push, to pray for it, without endangering ourselves, we could do nothing.''

He said that after the Hanne Knutsen managed to clear the Joy C, his attention returned to the Atalanta.

He added: ''After the Joy C my immediate concern was that we were quite close to the ship, that was quite an uncomfortable experience.''

Speaking of the Atalanta's position close to the Hanne Knutsen, he added: ''It hadn't occurred to me that it would have carried on that track having spoken to it.

''When I first saw the yacht it could have done anything it wanted to, apart from what it did - it could have gone east, west, north.''

He described how he saw the yacht become dismasted as it was in collision with the tanker, with its sail almost becoming entangled in the anchor.

He added: ''There was some carnage on board, there was a chap with a head injury, it came on the radio that someone had gone in the water but within seconds it came on he had gone down the starboard side and had been picked up.

''The lifeboat turned up in moments.''

Mr Lusty said it was his first time as marine officer that day having previously served as coxswain, but he said he had worked through several previous Cowes Weeks.

He said the Spitfire turned on its siren and flashing lights as it dealt with the incident.

Wilson denies failing to keep a proper lookout and two counts of impeding the passage of a tanker.

Charles Row, prosecuting, claims Wilson, who owned and skippered the 33ft racing yacht, sailed his boat, which had a crew of eight, into the path of the 42-metre wide Hanne Knutsen.

Mr Row said Wilson failed to comply with local shipping bylaws which required him to maintain a moving prohibited zone (MPZ) of 1,000 metres in front and 100 metres either side of a vessel greater than 150 metres long.