Flying LHR>MAN on BA, then have CX flight to HKG on same ticket (so will have boarding pass on my phone) and hand luggage only.

Is there airside transfer between T3 and T2 or do I need to leave and go landside? I read a post upstream from another forum
member which sounded like that they had to leave and then go back through security although not sure if that was a Covid related issue.
TIA