It would be better English to say 'The last person . . . '. Omitting 'the' puts it in the form of a terse instruction, that might for example be stuck on a notice board.
Thank you Clive. Would you tell me the grammar structure of last person to go? I saw it one the Lab door, it sounded so odd to me that I thought it might be wrong. Thank you very much for your help
eg The last person to leave was Tom = The last person who left was Tom. eg The last person to leave will be Tom = The last person who will leave will be Tom.
The last person to leave the office must lock the door. Subject....................................................... verb ............ object[ The last person to leave the office ] [must lock[ [the door].
The subject of the sentence is an infinite clause (phrase)
subject..................verbal (infinitive) ..... object [ The last person ] [ to l