Spanish Town is the site of an early cast-iron bridge, designed by Thomas Wilson and manufactured by Walker and Company of Rotherham, England. Spanning the Rio Cobre, the bridge was erected in 1801 at a cost of £4,000. Its four arched ribs are supported on massive masonry abutments. After the abutments deteriorated, endangering the structure, it was listed in the 1998 World Monuments Watch by the World Monuments Fund. A restoration project began in 2004, with funding provided by American Express through World Monuments Fund. Progress was slow until 2008, when a renewed restoration effort was made. A first phase of restoration was completed in April 2010, when the repair of the abutments allowed the bridge to be reopened for the public. More recently, violence in the area has prevented the bridge from achieving the status of a UNESCO World Heritage Site.
Question: How many years was the restoration project slow for?
Answer: 4