The Special Branch Registry is a filing system used by the Metropolitan Police. The Registry is where files on political activists, groups and other persons of interest to Special Branch are stored.
It was established in 1880 and in 1923 it became part of the central registry of the Metropolitan Police. However, in 1940 it was reorganised again as an independent registry.
In 1966, it had 300,000 open files on campaigning organisations, individuals and events. It has a parallel and to some extent overlapping counterpart in MI5's 'Personal File' system.
Since 2004 it has been referred to as the Intelligence Management and Operation Support (IMOS).
According to one witness in the Undercover Policing Inquiry, Alistair Pocock:
IMOS’ remit was and remains to record and administer intelligence received from all areas of the Metropolitan Police Special Branch (MPSB).
Registry (or Records) refers to the files themselves, while IMOS was the wider administrative body within MPSB that looked after them and related issues. It is separate to the wider General Registry held by the Metropolitan Police prior to computerisation. However, following re-organisations, the term IMOS is now used to refer to the legacy paper files and indices used to access them, rather than the unit itself.
Many of the files have since been destroyed in regular purges and reorganisations, though some were retained for historical purposes, or located in other archives, such as those of MI5. Some older files, mainly dating around, or prior to the Second World War are available via The National Archives.
With the advent of computerisation, the National Special Branch Information System (NSBIS) software was created to replace the paper-based file system and facilitate communication between different Special Branches. One instance of this software was the National Domestic Extremism Database.
The nature of record keeping within the Metropolitan Police Special Branch has been an issue within the Undercover Policing Inquiry. Several statements have been provided setting out its management system, particularly that of Alistair Pocock. Within the Metropolitan Police, Operation FileSafe was created to review the storage of material more generally, but with a focus on what was needed to be retained for the purposes of public inquiries.
Following a complaint in 2016 that material of interest to the Inquiry had been deliberately destroyed, the Inquiry sought assurances from the Metropolitan Police regarding this. For more on this and the related IOPC investigation, Operation Hibiscus, see under Assurance.
The Inquiry has refused to release files held on its core participants despite multiple requests, although it has released one document which states that in 1966 there were 300,000 in the Registry File system.