Fault occurred during the cold season on my 2003 Jaguar S-Type R. Engine went into limp mode, limited to 1000 - 2000 RPM.

Engine Systems Fault, Park Brake Fault, DSC Not Available.

The fault in this instance was traced to a faulty coil pack. Replacing the faulty pack resolved the issue. As per Andrew Downey's comment below, a common fault with the throttle position sensor can also cause these symptoms.