using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        var sampleBodyOrSummary = @"<p>People in the German city on <a href=""http://www.scenictours.co.uk/"">affluent river cruises</a> as well as people living in Cologne are expected to turn out in force when the Harry Potter exhibition comes to town.<br />";

        var result = Regex.Replace(sampleBodyOrSummary, @"(<a.*http:\/\/.*.scenictours.co.uk\/.+?>)(.*?)(</a>)", "$2");

        Console.Write(result);

    }

}