Its very material. If accuser and the accused were both pissed & drugged out their heads then neither can be relied upon to give reliable testimony.
Where there is a lack of any solid evidence or reliable witness testimony as evidenced in another recent celebrity case, the prosecution amasses evidence of supposedly similar crimes to provide the needed corroboration.
Indeed in the Salmond case this was exactly what came about under the so-called "Mooroví doctrine" where "The evidence of single witnesses to different incidents may provide what is known as mutual corroboration..."
The paucity of even this secondary "evidence" in the Salmond trial resulted in a lengthy charge list of absurdities the likes of: "...he flicked a curl in my hair..." which was deemed a "sexual assault".
The (majority female) Jury of course sensibly threw all this rubbish out, but in the case of self-confessed sex addict Brand, there will obviously be a far greater list of incidents to chose from under whatever English legal equivalent they dig up.
If this if the approach they take: and we can see the "Moorov" doctrine happening already in the present prurient "trial by media", then I would reckon Brand is toast.