It appears that the clutch slave cylinder leaked causing the loss of fluid. Whilst I have not been under the car to confirm this, I have noticed a patch of fluid where the car was parked over the weekend. The fluid loss must have been fairly sudden as the patch of fluid was not there previously. The car drove fine yesterday and this morning and there was no fluid loss under the car at work yesterday or at home last night. I will monitor the situation but it looks like I might be up for a new slave cylinder soon.

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107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.