Pushing a brake dust seal back in

[antnee]

HELP!! Any tips on how to push a brake piston seal back in?
Changing the pads on the rear, pushing the pistons back in and part (about 1/3rd) of the seal has decided to pop out from the main body to the piston. I am struggling to push it back into place!!

 

[dangerous dave]

Is that because your fighting the pressure as it's going back in?

Might need to whip the caliper off, clean up and try again on a bench...