This from the Directgov website
Reducing the period of a disqualification
You can ask the court to reduce the period of your disqualification after serving:
two years of the disqualification period if the disqualification was for more than two years but less than four years
half the disqualification period if the disqualification was for more than four years but less than 10 years
five years of the disqualification period if the disqualification was for 10 years or more
You’ll need to apply in writing to the court that disqualified you, giving the date of offence, date of conviction and any information to justify your request. If successful, the court will notify DVLA of the decision. You can then apply to renew your driving licence.
If the court refuses your request, you’ll have to wait three months before you can ask the court again.
Although it may be advisable to hire a solicitor to present your case.