Insect in food

We visited Mugg and Bean in Sunday 1 November for lunch. I ordered a chicken dish with salad. After waiting very long the food arrived. I was halfway through the meal then I saw a black insect - some sort of ****roach - crawling on my plate. I was do disgusted and sick. I had to run to the bathroom. We called the manager and waiter. The manager was very quick to take the plate away and came back with a weak apology. The meal was taken off from the bill. I refused to give a tip and then the waiter had to cheek to say it was not his fault. I blame all the staff that was on duty.