There is an easy way and a difficult way to remove the master cylinder.
The difficult way is to follow the manual which tells you to remove the torsion bar.

The easy way is as follows:
Remove the master cylinder floor cover.
Slacken the brake pipe tube nut, but DO NOT remove it completely.
Undo the banjo bolt from the rear of the master cylinder. It will work its way up the tube nut thread. When the two lock together, slacken the tube nut a little further, but still don’t remove it completely. Continue this process until the banjo bolt is out of the master cylinder.
Remove the nuts from both master cylinder bolts.
Using a large flat blade screwdriver under the head of one of the bolts, lever the torsion bar down. Remove the other bolt.
Using a large cross head screwdriver in the hole left by the removed bolt, lever the torsion bar down and remove the other bolt.

Assembly is a reversal of the above.

Unfortunately, not all cars allow the use of the above method. Build tolerances, particularly on later models, were not always as good as they should have been!

With this in mind, we have included the following from Peter Jones of Liverpool:

When I renewed my master cylinder I found it impossible to use a lever under one of the bolt heads to displace the torsion bar sufficiently to remove the other bolt. What I did, and found very easy, was to use a piece of chain around the torsion bar, of a size to fit between the chassis and torsion bar, and hanging down a short distance below the chassis. The chain may be joined using a suitable small shackle. Hold a piece of wood against the underside of the chassis then using the wood as a leverage point and the chain as a fulcrum, place a strong bar through the chain and under the wood and lever the torsion bar down to enable removal of both bolts. Two or three small shackles can be used instead of the chain. To make it easier next time!!! refit the bolts with their heads towards the middle of the car.
(Note from DSN Classics: We would not normally recommend the reversal of the bolts. However, if you you are absolutely sure that the clearance is sufficient, then it should be OK. The problem relates to build tolerances as mentioned above! )