Buy a good adhesive.
you can use GOOP or from B&Q - Evo Stik Serious Glue Fix & Repair Adhesive.
Step 1 - thoroguhly clean area to be repaired
Step 2 - apply adhesive generously
Step 3 - use cellophane tape or other tape tape it tight as possible
Step 4 - wrap it in one sheet of newspaper
Step 5 - put something heavy on it like several books
Step 6 - leave it for a few days to dry
Peter, September 2010