After coming back from Zolder 2007 oil pressure was significantly lower then it used to be; approximately between 30-40. Checked oil :was OK and I slightly topped up (0.5L)
The day after oil pressure was again normal for the car; around 60 psi?
The oli pressure sender often becomes unreliable; almost certainly the explanation - playing up due to the heat of a trackday but may be ok for a while now.
Not a difficult job to change if it continues to play up.