SDP or Tory?

We've received an email alleging that Robert Wilson, current Tory MP for Reading East and Shadow Minister for Higher Education, actually stood as an SDP candidate in Redlands ward in Reading in the the late 1980s. Which would make his denial to have ever been in the same party as Stephen Williams, during a debate on the 23rd January, a lie.

The only allusion we can find to this claim is on Wikipedia, which is hardly the most reliable source. Our tipster is adamant it's true. Does anyone know?