A brand of Ernest Jackson, who also brought you Victory V and Throaties, Mighty Imps, or just Imps as they are colloquially known are small (approximately 2x4x4mm), very strong liquorice pellets.
They came onto the market in 1923, intended to clear the throat. They combine Liquorice and Menthol, but contain no Aniseed.
They are still available from pharmacies, and officially come under the Medicated Confectionery banner.
I wonder if schoolkids still compete to see how many they can take at a time...?