The Malaysia Airlines Lounge Heathrow First Class lounge is a bit of an oddity, when you first think about it. With only four Business Class seats sold on the MH A350 LHR service with First access, why bother having a separate large lounge, with pre-flight dining and bar. And buffet. And showers. Particularly as Malaysia has closed almost all of it's outstation lounges.
The reason is it's a historical leftover, from when Malaysia's A380 first started flying 15 years ago, and the lounge had a revamp.
However, it's there, and does have all the perks, for the few oneworld Emeralds who can take advantage.