Originally Posted by RayG

While I generally think SQ has a very liberal and customer friendly interlining policy, SQ was unable to check through my luggage with a connection at LHR.

In my case, I was flying Suites into LHR on SQ and connecting to T5 on BA. Luggage allowance on either carriers nor connection time was the issue. I was advised at the SIN F check-in reception (as well as also speaking during check-in to the SQ back-office) that there was a LHR "airport" restriction preventing SQ to connect to BA in LHR. In fairness, this was in 2023 (I didn't bother asking for my LHR bound SQ flights in 2024).

But give it a try, ask at AKL and let us know.