The period from the mid-14th century to the 19th century in Europe has been called the "Little Ice Age" because of how severe the climate was, and it was during this time that the fairs took place. However, this wasn’t the only reason why the river froze.

The Thames was much wider and shallower then which meant it flowed more slowly. Also, the old London Bridge had 19 narrow arches which hampered the river's flow, making freezing more likely. It turned to ice more than 20 times before 1814. 

Although the first recorded frost fair didn’t happen until 1608, the river did freeze over many times in the 1500s and obviously had the royal seal of approval. Henry VIII is said to have travelled all the way from central London to Greenwich by sleigh along the river during the winter of 1536, and Elizabeth I took walks on the ice during the winter of 1564.

Frost fairs could never be predicted, but when they did happen they were amazing spectacles and people took full advantage of the ice by setting up stalls and sideshows on it. There were fairground attractions, merry-go-rounds, swings, puppet shows, skittles, football and bowls.  Donkey, horse and wagon racing events also took place.

The fairs on the Thames are well documented by artists, and the two most famous seem to have been held in these years: 

1683-84

This is how diarist John Evelyn described the festive but particularly cold fair of this year, where the ice was 11in thick in some places:

"Coaches plied from Westminster to the Temple, and from several other stairs too and fro, as in the streets, sleds, sliding with skates, bull-baiting, horse and coach races, puppet plays and interludes, cooks, tippling and other lewd places, so that it seemed to be a bacchanalian triumph, or carnival on the water."

Cashing in on the carnival atmosphere was Croom the printer who sold souvenir cards written with the customer's name, the date, and the fact that the card was printed on the Thames, all for six pence, proving over-priced souvenirs are nothing new! He was said to be making £5 a day from this canny venture, which was at least ten times a labourer's weekly wage. Even King Charles II bought one when he and his family visited.

1813-14

This winter saw what is considered to be the greatest frost fair – a huge event where the main "road" was named City Road and went straight down the middle of the Thames, rather than across, with stalls lining it. The fair lasted four days. 

As word got round, the fair attracted more and more visitors. Entertainment included swings, book stalls, skittles, dancing-booths, merry-go-rounds and donkey rides and then the place was crawling with pedlars, book sellers, toy sellers, and anything labelled with the words "bought on the Thames" could be flogged for a high price.

An exotic flavour was added when an elephant was led across the river below Blackfriars Bridge, and a printer named Davis published a book, elaborately called Frostiana; Or A History Of The River Thames In A Frozen State.

Although fun for many, the freezing of the Thames was a tragedy for boat skippers who could not move in or out of the port and so found themselves out of work. Some watermen made the best of the situation by making sure no one had access to the Thames without their help. They assisted people over channels they had made in the ice and charged them a fee for the privilege! But as trade ground to a halt, coal and many other goods became scarce.

Eventually rain set in which began to crack the ice and ended the last London frost fair. The climate was growing milder and Old London Bridge was replaced in 1831 with John Rennie’s new design. It had far wider arches which improved the flow of the river making it impossible to freeze over and play host to London’s carnival on ice.