Yes Sir, no Sir, not much difference Sir

To assess whether making the sender's knighthood explicit in a series of letters would have any detectable effect on the response.

A random sequence was generated by flipping a coin to determine whether a letter would have 'Sir Iain Chalmers' or 'Iain Chalmers' typed under the signature. This sequence was prepared independently of the preparation of an alphabetic list of the intended recipients and was then used to determine which letter would be sent. The allocation could not be influenced by prior knowledge of the recipient. Two batches of letters were sent.

Medical royal colleges and associated faculties, and postgraduate medical and dental schools in the UK.

Presidents and deans of medical royal colleges and deans of postgraduate medical and dental schools in the UK.

Rates of response and the mean number of days between the posting of the original letter and the date on the response.

No differences between the groups were detected in the response rates: 91% and 90% for 'Sir Iain Chalmers' and 'Iain Chalmers' (relative rate for response of 1.01, 95%CI 0.83-1.23, P = 0.92), or in the mean number of days to response ('Sir': 32 days; 'no Sir': 33 days).

This finding is consistent with a systematic review of responses to postal surveys, in which the effect of the status of the signatory was investigated. Combining our result with the two trials that are most comparable to our study, in which letters from professors were compared with letters from students, gives a relative response rate of 1.00 (95% CI 0.91-1.10, P = 0.99). There is, therefore, no evidence from the existing randomized experiments that the status of the signatory has any impact on the likelihood or promptness of response-even if the status was conferred by the British monarch.