Simplify the following text for a Grade 11 native English-speaking person.
Original: Under Michael Howard , Johnson briefly served on the Conservative front bench as the Shadow Minister for the Arts from April 2004 until November 2004 when he was sacked after allegedly lying to Howard when denying he had had an affair with Petronella Wyatt .
Simplified: Under Michael Howard , Johnson briefly served on the Conservative front bench as the Shadow Minister for the Arts from April 2004 until November 2004 .