Expansion assembly, top anchor and method for expanding a tubular in a wellbore

An expansion assembly for expanding a tubular in a wellbore, the expansion assembly including a top anchor comprising: a workstring; a pusher ring being coupled to the workstring by a first releasable coupling; a ramp body having one or more ramp surfaces, said ramp body being releasably coupled to the workstring by a second releasable coupling; one or more anchor segments each having one or more wedge surfaces corresponding to and engaging the ramp surfaces of the ramp body, one end of the segments engaging the pusher ring; a release ring enclosing the workstring and arranged at an opposite end of the segments; one or more key merlons connecting the release ring to the pusher ring; and activating means for releasing the first releasable coupling.