At some point the brake pedal felt rather different, it returned far more slowly. At first I suspected air in the system, but after bleeding it still felt the same.
Sometime later I remembered that a Lotus Technical Service Bulletin mentioned this problem and suggested the addition of a brake pedal return spring. Apparently my Esprit did have this spring but somehow it got disconnected. After an inspection, I found it in the carpet of the footwell. Once reinstalled the brake pedal felt as usual again.
Here is the text from the Lotus TSB (#9):
Modifications to improve stop lamp switching.
It has been found that the brake pedal on some Esprit models can become, due to a variety of factors, reluctant or lazy in returning fully to its' off position. In such cases, the stop lamp switch may remain closed (brake lights on), and an ABS fault code A034 may be set.
In order to improve the consistency and reliability of stop lamp switch operation on such cars, the spring pressure of the stop switch plunger can be reduced, and a brake pedal return spring added. These revisions may be incorporated on any Esprit model with anti-lock brakes where such symptoms are experienced.
If any ABS equipped Esprit model is found to exhibit symptoms of the brake lights staying on, or if an ABS fault code A034 is set, refer first to Service Notes section JF.l7 (Date 1995/ 0l) to check the brake pedal height and stop switch adjustment. If the symptoms are still apparent, carry out the following modification:
Parts Required: Brake Light Switch (modified) A082M50115 1 off and Brake Pedal Return Spring A082J43975 1 off
1. Disconnect and remove (twist 1/4 turn counterclockwise) the stop switch.
2. From the stop switch mounting bracket on the pedal box, press out the plastic stop switch bush. Using a small round file, make a shallow groove in the top notch in the bracket, of sufficient depth to anchor the new return spring. Refit the bush.
3. Hook the round loop of the new brake pedal return spring into the bracket groove, and hook the other end around the front of the brake pedal.
4. Fit the modified stop switch into the bracket and adjust as detailed in Service Notes section JF.l7.
Note that in order to prevent over stretching, the spring should be disconnected before a brake bleeding operation. !!!!!!!