I will be flying from New Delhi to Manchester soon and my return dates aren't fixed yet. Do I need to show a return ticket to the immigration officer when asked at the port of entry?
Do I need to show a return ticket to the immigration officer when asked at the port of entry?
No. UK does not require proof of return/onward travel as a matter of routine and if you don't have such a ticket you can't produce it on request at a border.
However, it is not very likely that you will be asked for a return ticket unless there is some doubt about your returning and then having a return ticket should help. So (a) it would be sensible to have one if you can and (b) you must definitely show it if asked and you do have one. Denying you have such a ticket that then turns up during a search is an invitation to be sent straight back to wherever you came from.
Depending upon your circumstances you may be able to persuade the IO that, while it is certain you will depart UK in good time, there is a good reason you have deferred purchase of your return ticket. This might be that you will return home directly unless you hear within a few days that you are invited to speak at a conference in Country X in a fortnight, so would in that case book your return via Country X rather than direct.