We present high-resolution , time-resolved optical spectroscopy of the black hole X-ray transient Swift J1753.5-0127 .
Our optical spectra do not show features that we can associate with the companion star .
However we do observe broad , double-peaked emission lines , typical of an accretion disc .
We show that the mass of the compact object is likely > 7.4 \pm 1.2 M _ { \odot } , much higher than previous suggestions of a low-mass ( < 5 M _ { \odot } ) black hole .