Here's a short story:

Brighton is a seaside resort on the south coast of England. It is part of the city of Brighton and Hove and the ceremonial county of East Sussex, within the historic county of Sussex. 

Archaeological evidence of settlement in the area dates back to the Bronze Age, Roman and Anglo-Saxon periods. The ancient settlement of "Brighthelmstone" was documented in the "Domesday Book" (1086). The town's importance grew in the Middle Ages as the Old Town developed, but it languished in the early modern period, affected by foreign attacks, storms, a suffering economy and a declining population. Brighton began to attract more visitors following improved road transport to London and becoming a boarding point for boats travelling to France. The town also developed in popularity as a health resort for sea bathing as a purported cure for illnesses. 

In the Georgian era, Brighton developed as a fashionable seaside resort, encouraged by the patronage of the Prince Regent, later King George IV, who spent much time in the town and constructed the Royal Pavilion in the Regency era. Brighton continued to grow as a major centre of tourism following the arrival of the railways in 1841, becoming a popular destination for day-trippers from London. Many of the major attractions were built in the Victorian era, including the Grand Hotel, the West Pier, and the Brighton Palace Pier. The town continued to grow into the 20th century, expanding to incorporate more areas into the town's boundaries before joining the town of Hove to form the unitary authority of Brighton and Hove in 1997, which was granted city status in 2000. (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: What is the name of this place?
Guess: Brighton

Question: What is it?
Guess: a seaside resort

Question: Where?
Guess: England

Question: Which part?
Guess: on the south coast

Question: Which county is it in?
Guess: Sussex

Question: How long has it been inhabited by people?
Guess: the Bronze Age

Question: Any other periods?
Guess: Roman and Anglo-Saxon

Question: What is the first reference of it?
Guess: The ancient settlement of "Brighthelmstone"

Question: Where was that found?
Guess: in the "Domesday Book"

Question: When?
Guess: 1086

Now answer the following question in the same format.

Question: When did it become an important place?

in the Middle Ages