He was told quite recently that they had been taped over as a matter of routine, which does sound highly implausible.
Times, Sunday Times (2010)
It now sounds highly implausible.
Times, Sunday Times (2015)
I find this view of language highly implausible.
Times, Sunday Times (2011)
The plot has some highly implausible twists, too.
Times, Sunday Times (2011)
When she visited a psychic for research purposes she found it highly implausible.
Times, Sunday Times (2007)