Hole patterns are common in engineering design for connections and/or assembly purposes. Geometrical discontinuities can cause stress concentration in localized areas, making them more prone to fatigue crack initiation and influencing the fatigue life of the overall unit. In the past, much effort has been exerted on fatigue modelling of holed plates from both experimental and theoretical perspectives. However, most studied objects were aluminium or titanium thin plates for aviation purposes. In this work, the fatigue performance of a downscaled holed thick steel plate, extracted from a novel C1 Wedge Connection for wind turbine tower assembling, was tested and categorized according to commonly used industry codes. In particular, the influence of the surface size effect was experimentally observed and computationally discussed. Finally, a probabilistic fatigue model was proposed, which gives a favourable prediction on the fatigue behaviour of the surface polished holed thick steel plate with the help of the Smith–Watson–Topper (SWT) model.