, 1 June 2013 (UTC) .... Afterthought, it occurs to me that the older term in the UK for 'check in', is 'sign in' , therefore it would not be unusual when arriving at a hotel, to be asked to 'sign in (to the hotel register)' ... one could not meaningfully 'sign into the hotel register' (unless one were waving one's pen around in the approximate direction of the outside of the register) ... does this not illustrate that there cannot be a hard and fast rule about the appropriateness of in to/into ?  17:30