It is a popular myth that India Pale Ales were made stronger than regular beers in order to assist them to survive the ardours of long sea travel. Export beers were more heavily hopped, but not necessarily stronger. If you want proof, here it is, an IPA from 1914 at only 4.2%. This predates the imposition of wartime restrictions on drink supply and strength, so was a commercially available beer of the day.

Tommy has a bitterness of 60 IBUs, but this is softened by a high final gravity that gives a full-bodied sweetness to the beer that accentuates the orangey notes lent to the beer by large quantities of Kentish WGV hops, making it a big beer in terms of flavour and character rather than merely alcoholic strength or raw bitterness alone. In other words, what an authentic IPA was once really like.