The appointment is the final nail in the coffin for KBK, which will close next month. The founding partner Simon Kershaw left two weeks ago to become the executive creative director at the direct marketing agency TDA.
Kershaw's departure came just a month after his fellow partner Steve Barton left the agency without a job to go to.
Keevill said: "We will be informing our clients today and tomorrow, but we will be shutting down at the end of July."
The appointment sees Keevill take on the role of art director, alongside the agency's co-founder and creative partner, Paul Kitcatt. Keevill is Kitcatt's first full-time creative partner since the shop was founded five years ago.
Kitcatt said: "When a creative Titan like Phil becomes available, you would be crazy not to act."