While a cake with dried fruits honey and nuts in it can be traced back to ancient times, the fruitcake as we know it probably began in the Medieval Ages. It was only in the thirteenth century that dried fruits began to arrive in Britain, and they were very expensive. http://www.foodtimeline.org/christmasfood.html
Making a rich fruit cake in the 18th century was a major undertaking. The ingredients had to be carefully prepared. Fruit was washed, dried, and stoned (taking the pits out) if necessary; sugar, cut from loaves, had to be pounded and sieved; butter washed in water and rinsed in rosewater. Eggs were beaten for a long time, half an hour being commonly directed. Yeast, or barm from fermented beer, had to be coaxed to life. Finally, the cook had to cope with the termeramental wood-fired baking ovens of that time.
Oxford Companion to Food
Alan Davidson (Oxford University Press: Oxford) 1999 (p. 321-322) No wonder fruitcakes were reserved for holidays, special events and celebrations. For a five star rated contemporary recipe see: http://www.foodnetwork.com/recipes/alton-brown/free-range-fruitcake-recipe/index.html