Documents in a recently revealed British archive include 110 categories concerning Hong Kong, according to an inventory of the facility. They relate to a British intelligence organisation in the city, and cover discussion of the territory's future in the 1980s and 1990s and immigration issues, among other matters.
The archive at Hanslope Park, a high- security government communications centre in Buckinghamshire, is estimated to hold about 1.2 million files on British foreign relations. These files are divided into some 2,000 categories, and 110 of them are regarding Hong Kong.
If the files were stacked, they would tower more than 80 metres high.
Many of the documents should have been made public after 30 years, according to the Public Records Act, but have remained secret.
The inventory shows some files about a British intelligence organisation in Hong Kong were created in the turbulent period between 1963 and 1968.
There are also immigration files from the 1960s to 1990s, Executive Council proceedings from as early as 1959 and colonial reports dating back to 1845. Files about Hong Kong's future include documents on the British National (Overseas) passport, defence and financial issues.
In response to inquiries by the Sunday Morning Post, Britain's Foreign Office said a prioritised plan for the review and release of files in the archive would be presented to the Lord Chancellor's Advisory Council on National Records and Archives on Thursday.
City University professor Ray Yep Kin-man said their release would be especially helpful for anyone studying negotiations between Beijing and London on Hong Kong.
He said such studies currently relied mainly on the biographies of former Beijing officials and limited documents from Britain about the late governor Murray MacLehose and the late British prime minister Margaret Thatcher.
"There's not much information now," he said. "The Chinese side doesn't talk much about it, and … the release of documents is random. Some Hong Kong files were even taken away."
Professor Robert Bickers, from Bristol University's history department in Britain, said although many files looked like routine government documents, some could be more sensitive.
"It may have been thought that this was material that might compromise individuals still living in Hong Kong," he said.
"It should come as no surprise to find that various categories of potentially diplomatically sensitive material were exported before the handover.
"Colonial Hong Kong was increasingly subservient politically to UK-China relations from the late 1960s onwards."
Bickers said it was also important to note that some important files were not in the archive.
"Don't rush to assume that UK government departments are wholly competent about conforming to UK archives law, or have the personnel capacity to meet their legal obligations. They clearly don't," he said.