LATEST: Christie Brinkley has filed for divorce from her fourth husband, architect Peter Cook, after 10 years of marriage. The couple announced they were separating in July (06) after Cook's affair with his 18-year-old assistant was revealed. Cook's attorney NORMAN SHERESKY has confirmed that his client has now been served with a summons, which is the first step in moving forward with a divorce. Sheresky tells American publication People, "The next step would be for (Brinkley) to serve a complaint and/or for the parties to negotiate an amicable agreement." Sheresky's business partner, DAVID ARONSON says Cook is distraught over Brinkley's decision to go ahead with the divorce. He says, "He was hopeful that they would be able to work through this and continue their marriage. "He is saddened by the fact that she has decided to move forward, but he understand that's her right and he will respect that." When asked if Cook hoped to reconcile, Aronson says, "Absolutely. He made no bones about that to her and the few times he's spoken to the press. "He hoped they would work through their problems and continue with their life together. He loves his children and family."