When he was a child, Gregg loved playing with toy trainsets. Now he's got special access to learn how the ultimate model is made: a huge 187 tonne, five carriage electric train. Meanwhile, Cherry Healey travels to Scotland to visit the UK's last remaining factory that produces aluminium via smelting. Historian Ruth Goodman is energised by the history of electric trains as she learns that the UK's first was a tourist train that is still in use along the Brighton seafront.