Pre-heat the grill to a medium-to-high setting. Fry the onion in the olive oil for 2 minutes over a high heat. Add the pepper and fry for 5 minutes on a medium heat. Remove pan and add the tomatoes, ham and sweetcorn.
Place the pancakes on a greased baking sheet. Spoon on the filling and fold up the edges to enclose it. Top with cheese and grill for 5 minutes or until the cheese melts. Top with the relish and sliced gherkin.