This paper reports on experiments on a pseudo four tidal stream turbine array. This was achieved by towing two side-by-side turbines adjacent to the sidewall of a tow tank, which acted as a symmetry plane. The 1.2 m diameter (d) rotors were tested with d/4 tip-to-tip spacing at SSPA in Sweden through the MaRINET2 Transnational Access Programme. Tests at different tow speeds demonstrated that in low onset turbulence 0.9 m/s was required to achieve Reynolds number independence, higher than the 0.8 m/s required for the same turbines at the FloWave Ocean Energy Research Facility in higher ambient turbulence. Cross-fence variation in turbine performance indicates that the tank sidewall acted as a symmetry plane as desired. Power and thrust coefficients are consistently 1-2% higher for the inboard rotor, and increased blade loads associated with blade passage past the neighbouring turbine were observed, demonstrating constructive interference effects between the two rotors.