The man had met with two men in the Canal Street area before walking towards Back Piccadilly, where he was then raped and robbed.
After the attack, it is believed the offenders met up with a further man before all three travelled via Birmingham and London Victoria on the National Express Coach, arriving in London around 6am.
Since the rape occurred, officers have been examining CCTV footage to establish the circumstances surrounding the offence.
CCTV images released by investigating officers show three men they want to speak to in connection with the investigation.
Detective Constable Louise Kelly of GMP’s City of Manchester division, said:
“Since the attack, we’ve been following numerous lines of enquiry, but unfortunately we have yet to find the men responsible.
“We have now released images of three men we want to speak to.
“Anyone who recognises these men should get in touch with us as soon as possible.
“We urge people to pass on any information, no matter how small, so that we can progress this investigation further.”
Anyone with any information should contact police on 0161 856 4409 quoting reference 133 03/04/19 or the independent charity Crimestoppers, anonymously, on 0800 555 111.