Is it plausible that information over a century old could be withheld under FOIA on the grounds of national security and/or endangerment of health and safety? The answer is evidently ‘yes’. That was the outcome of a request for information on informants in the Jack the Ripper investigations (see Marriott v IC EA/2010/0183). A request for information on police informants involved in Irish secret societies over the period 1890-1910 has met the same outcome.
In Judge Wikeley’s recent judgment in Keane v IC, Home Office and Metropolitan Police Service  UKUT 0461 (AAC) (keane-ut), the Upper Tribunal has upheld a First-Tier Tribunal decision that such historical informant-related information should not be disclosed. This was essentially because the recruitment and retention of current informants would be undermined if informants lost confidence that their anonymity would be preserved well after their death.
Judge Wikeley had some reservations about the FTT’s decision, but declined to unpick it via excessively minute textual analysis.
He did, however, offer thoughts on the broad question ‘how long is long enough?’ – for example, it would be a bit of a stretch to withhold equivalent information dating back to the English Civil War.
Oh, and Judge Wikeley’s judgment includes a prologue comprising an extract from Joseph Conrad’s novel, The Secret Agent.
11KBW’s Rupert Paines, Chris Knight and Andrew Sharland all put in appearances in Keane.