When I'm on form, I take sarnies (cheese, or mushroom pate), and a piece of fruit, maybe an Empire apple (regrettably American, but otherwise close to apple perfection). Back in the old days, the sarnies had ham or pastrami or low-fat Ardennes pate in.

Sometimes I took in bought pots of pasta salad or couscous or whatever - some sort of starch salad at any rate, but they cost too much and I'm forgetful. OTOH I've been thinking about making some pasta pesto up the night before, and taking a tub in to eat cold.

Really ages back things such as crisps and pork pies and sausage rolls and cereal bars and small cartons of california raisins etc. etc. etc. also found their ways into lunches.