It must be said that many of my foreign informants found this aspect of Englishness frustrating,

[cunctator_]

rather than amusing: ‘The problem with the English,’ complained one American visitor, ‘is that you never know when they are joking - you never know whether they are being serious or not’. This was a businessman, travelling with a female colleague from Holland. She considered the issue frowningly for a moment, and then concluded, somewhat tentatively, ‘I think they are mostly joking, yes?’

Watching the English: the hidden rules of English behaviour by Kate Fox