Calais oil leak

The oil is probably coming from the rear main oil seal on the crankshaft. It's relatively common and shouldn't be of great concern providing it's not a large pool of oil. Check the engine oil level regularly and if you see it dropping rather quickly have a mechanic check the leak. There are anti-rattle washers in the brakes and they are sometimes lost or not replaced when the brakes are serviced, so have a brake specialist check them for you.