Malaysia’s “new evidence” that it has sovereignty – and not its southern neighbour Singapore – over the rocky outcrop called Pedra Branca comprises a letter by Singapore’s top colonial official in 1958, a naval incident report the same year, and a map of the Lion City in 1966, This Week in Asia has learnt.

These three documents would likely overturn the decision by the International Court of Justice in 2008 to award sovereignty to the disputed island to Singapore, Malaysia claimed in court documents filed on February 3.

“This application is not an appeal against the 2008 judgment. On the contrary, it draws to the court’s attention what has only recently become known to Malaysia, namely, that even after the 1953 correspondence, and at a point at which Singapore had become a self-governing colonial territory, Singapore, at the highest levels of its government, did not have the view that it had sovereignty over Pedra Branca/Pulau Batu Puteh,” said court documents seen by This Week in Asia.

“Singapore subsequently carried this appreciation into its federation as part of Malaysia in 1963, and, as it necessarily follows, that appreciation remained controlling on Singapore’s independence in 1965,” the documents said.

“It is Malaysia’s contention, informed by a close reading of the judgment in 2008 and its accompanying opinions, that the court would have been bound to reach a different conclusion on the question of sovereignty over Pedra Branca had it been aware of this new evidence.”

Malaysia on February 3 filed for a revision to the International Court of Justice’s ruling in 2008 that the isle of Pedra Branca, a football-field sized rocky outcrop, belongs to Singapore.

Malaysia reopens Pedra Branca island row with Singapore after a decade

The isle, which is called Pulau Batu Puteh by Malaysia, is about 40 kilometres from Singapore and 19 kilometres from the coast of Malaysia’s southern state of Johor.

The Horsburgh Lighthouse, built by Britain in 1851 and subsequently maintained by colonial and then Singaporean officials, is located on the isle. The outcrop is located at a strategic point, at the eastern approach to the Singapore straits from the South China Sea.

The 2008 ruling ended a decades-long dispute that began when Malaysia published a map in 1979 depicting the isle within its territorial waters.

The court’s 2008 decision had placed significant weight upon a 1953 letter from the acting colonial secretary in Johor to Singapore officials indicating the state did not stake a claim to the isle.

In its latest filing, Malaysia said a confidential telegram in 1958 sent by the then Governor of Singapore to the secretary of state for the colonies in London showed he “did not consider the island of Pedra Branca/Pulau Batu Puteh to be part of Singaporean territory”.

The governor had proposed the establishment of an international high seas corridor passing “only one mile from Pedra Branca/Pulau Puteh”.

“If he had understood, or otherwise been advised, that Pedra Branca/Pulau Batu Puteh was under Singaporean sovereignty, there would not have been a need for him to advocate the provision of an international passage so near to the island,” Malaysia’s filing said.

The second document is a naval incident report that showed that British naval vessels – assigned to defend Singaporean waters – “did not view the waters around Pedra Branca/Pulau Batu Puteh as belonging to Singapore”. The incident report, addressed to the Governor of Singapore, said a British naval vessel could not assist a Malaysian vessel being followed by an Indonesian gunboat as it “was still inside Johor territorial waters”.

The third article is a map dated 1962 but with markings dated February 1966 that the Malaysian filing said showed Singapore’s territorial waters “do not extend to the vicinity of Pedra Branca/Pulau Batu Puteh”.

The filing said Malaysia conducted research at the British archives between August 4 last year and January 30 this year.

Singapore attained independence as a sovereign nation on August 9, 1965, after a tumultuous two-year union with Malaysia.

Singaporean officials last week said they were reviewing Malaysia’s application and had assembled a legal team comprising the key members who led the 2008 legal battle.

They include former Deputy Prime Minister S. Jayakumar, former Chief Justice Chan Sek Keong, ambassador-at-large Tommy Koh and Attorney General Lucien Wong.

Malaysia’s application will need to satisfy Article 61 of the ICJ’s statute, which specifies criteria that need to be met before a revision to an earlier decision is made.