CJT94

Looking for some advice, every time it rains my rear passenger footwell floods really badly. Took approx 6 litres of water out yesterday. Can’t seem to find the source and wandered if there are any areas that are prone to leaks? The water seems to appear from nowhere, the door seals, window seals, A/B/C pillars, boot, front footwells and roof linings are all bone dry. Even the footwell above the ankle level are dry, indicating water isn’t coming from the door area. The water gets in even with the car being stationary. The only two things I can think of are the sunroof drains (as I believe they expel water in the region of the rear footwells) or the aerial (but would assume both footwells would have some water in, not just the passenger side) any pointers would be much appreciated as it seems to be getting gradually worse. TIA.