Supermaxi Investec Loyal charged down five-time winner Wild Oats XI to claim her first Sydney to Hobart title yesterday, but an official challenge means the victory could be short-lived.

The 100-footer took line honours with a slender margin of just three minutes and eight seconds – one of the closest finishes in decades – but it was soon overshadowed by claims Investec had received unauthorised outside assistance.

Cruising Yacht Club of Australia commodore Garry Linacre said Investec would have to face an international jury today over allegations it had asked a media helicopter crew what kind of sails Wild Oats had up earlier in the race.

“It’s against a racing rule of sailing, number 41,” Linacre told reporters.

When asked whether Investec could be disqualified if found guilty he said: “I would say that the answer to that question would have to be yes.”

“It’s a disappointing situation for me,” he added.

Thousands of onlookers had cheered at Hobart’s Constitution Dock as 2010 runner-up Investec crossed the line in a time of two days, six hours, 14 minutes and 18 seconds to claim its first line honours win.

The two supermaxis have long been rivals in the blue-water classic.

Linacre said the crew had been served with protest papers as they stepped ashore and “I would imagine that this was as much of a shock to them as it is to me.”

Investec skipper Anthony Bell said the question about sails had just been “a question of are they alright and have they lost any mainsails” following rough conditions on the first night which saw a number of boats retire.

“We respect the fact that there’s laws in racing... and we will, of course, go in and oblige that, and we’re confident that the outcome will confirm our win,” Bell told reporters.

“One thing that can’t be taken away from us is that we raced one hell of a race out there, and we did everything by the book.”

Aside from disqualification, Investec Loyal could instead face a time penalty or other sanctions deemed appropriate by the four-nation jury after hearing evidence and related arguments from both sides.

According to the protest, the incident at 6.30 a.m. on Tuesday involved a “crewman from Investec Loyal seeking information from the helicopter of the sail plan in use on Wild Oats XI.”

Investec had never been far from Wild Oats’s tail on the famously gruelling 628-nautical mile dash down Australia’s east coast, and their patience finally paid off Tuesday night when they overtook the race favourite for the first time.

A cat-and-mouse game ensued throughout yesterday’s gripping final day, and 45 minutes from the line Investec’s crew reported: “10 nautical miles to go and it’s going to be close. Wild Oats is right behind and in sight.”

It is the second time in as many years the race finish has been dogged by controversy, with Wild Oats facing a similar challenge last year for failing to have an operational high-frequency radio at the entrance to the Bass Strait.

That requirement was introduced after the catastrophic 1998 edition of the Sydney to Hobart which claimed the lives of six sailors and sank five boats.

Wild Oats was ultimately confirmed as line honours winner in 2010 after the protest was dismissed.