The conviction became spent after 5 years (unless you were under 18 at the time, in which case it became spent after 2½ years):
http://www.lawontheweb.co.uk/rehabact.htm
If an employer (other than as below) asks you a direct question [e.g. Have you ever been convicted of a criminal offence?] you're allowed to 'answer accordingly' (i.e. lie and say 'No'). The same applies to indirect questions, where a truthful answer might give away your conviction.
However some types of employment are exempt from the provisions of the Rehabilitation of Offenders Act. They are principally jobs working with, or alongside, children or vulnerable adults. (Jobs related to the 'administration of justice' are also exempt). So if, for example, you applied for a job as a teacher, school caretaker, nurse, hospital porter or care worker you would be required to disclose your conviction.
Chris