Yes, Minister, Series Three (1982)

Hacker:
How am I going to explain the missing documents to the Mail?

Sir Humphrey:
Well, this is what we normally do in circumstances like these.

[passes Hacker a memo]

Hacker:
"This file contains the complete set of papers, except for a number of secret documents, a few others which are part of still active files, some correspondence lost in the floods of 1967..." Was 1967 a particularly bad winter?

Sir Humphrey:
No, a marvellous winter. We lost no end of embarrassing files.

Hacker:
"...Some records which went astray in the move to London and others when the War Office was incorporated in the Ministry of Defence, and the normal withdrawal of papers whose publication could give grounds for an action for libel or breach of confidence or cause embarrassment to friendly governments". That's pretty comprehensive. How many does that normally leave for them to look at?