This paper presents a comprehensive performance analysis of the optimal widely linear (WL) minimum variance distorsionless response (MVDR) beamformer for the reception of an unknown signal of interest (SOI) corrupted by potentially second order (SO) noncircular background noise and interference. The SOI, whose waveform is unknown, is assumed to be SO noncircular with arbitrary noncircularity properties. In the steady state and for SO noncircular SOI and/or interference, this WL beamformer is shown to always improve the signal to interference plus noise ratio (SINR) and the symbol error rate (SER) performance at the ouput of both the well-known Capon's beamformer and a WL MVDR beamformer introduced recently in the literature