What's the best excuse do you suggest to mention in a Leave letter?

It sounds to me like you need an excuse that you can use again and again. The trick is to keep things simple, and to make sure that it is something that cannot be disproven. Family crises are good for such things.

Nobody would fault you for visiting a sick relative - and the closer that person is to you the more times you would be able to visit them. The graver the illness, the less likely they are to question you about it. Of course, I have always found that honesty is the best policy.

If you tell the truth, the worst that the boss can say is no, and there is no chance that you will ever get caught.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.