labialisation การใช้

If either of the two was voiceless, the whole cluster was devoiced, and the first obstruent also lost its labialisation, if it was present.
Either by looking up Estuary English, or by looking up Elmer Fudd, Bugs would have been presented with links to R-labialisation and rhotacism.
He also would have seen that Estuary English features L-vocalisation, but typically doesn't feature the r-labialisation the OP asked about.
Linguistic reconstructions suggest that both the richness of the consonantal systems and the poverty of the vocalic systems may be the result of a historical process, whereby vowel features such as labialisation and Proto-NWC.
Historically, it was unclear whether the labiovelar row represented an innovation by a process of labialisation, or whether it was inherited from the parent language ( but lost in the satem branches ); current mainstream opinion favours the latter possibility.