The most useful history skill is asking "how do we know?" A quick way to teach it:

1. Made at the time: a letter, a coin, a photo, an inscription.

2. Written later: a history book, a memoir decades on.

3. Scientific finding: what tests on bones, soil or ice show.

PastRush: History Detective launches here on 5 November. I'm one of the makers.

Each investigation is a case file with labelled exhibits. You put events in order, compare sources, trace causes and decide what the evidence can and can't prove. Six are free: the Rosetta Stone, Pompeii, the Grand Canyon's rock layers, tzi the Iceman, continental drift and the Norse in Vinland.