Final answer:
During the English Civil War, the Cavaliers were the royalist supporters known for their long hair and fashionable clothing, in contrast to the Roundheads who were aligned with Parliament.
Step-by-step explanation:
The long-haired, dandyish supporters of the king during the civil war were known as Cavaliers. These royalist supporters were characterized by their elaborate and fashionable dress, which often included long hair and luxurious clothing, standing in opposition to the more plainly dressed and short-haired Parliamentarians, also known as Roundheads. This distinction between the two sides was symbolic of the larger cultural and social conflicts that were part of the English Civil War.