John C. Sullivan is Of Counsel at London Fischer, LLP and an insurance coverage and complex commercial litigator who advises and defends insurers and policyholders in high-exposure matters. He focuses his practice on Directors & Officers (D&O), Professional Liability (including E&O), Commercial Crime, and Representations & Warranties (R&W) insurance disputes, with particular depth in R&W matters arising from M&A transactions across a range of industries.

John has substantial experience across the litigation lifecycle—from early case assessment and strategy through pleadings, discovery, depositions, motion practice, and trial support. In the R&W space, he counsels insurers on coverage positions from initial claim intake through resolution, including matters involving alleged breaches of financial, operational, and compliance representations in acquisition agreements. He has practiced extensively in New York, including trial in the New York Commercial Division, and appellate advocacy before the New York Appellate Division, First Department.

Before joining London Fischer, John practiced insurance coverage litigation at several firms where he defended and advised insurers in complex D&O, professional liability, and R&W matters and provided frequent coverage counseling.

John is known for delivering practical, business-minded coverage guidance grounded in litigation realities. He routinely manages a high volume of active matters simultaneously and drafts coverage opinions and key coverage correspondence—including reservations of rights and disclaimers—on a near-daily basis. He also works closely with claims professionals and stakeholders to align coverage positions, litigation strategy, and business objectives, and he supervises junior attorneys while managing eDiscovery and vendor workflows to promote efficient, cost-effective outcomes.

Notable Decisions / Representative Matters

  • Represented an insurer in an R&W coverage dispute stemming from a DOJ antitrust investigation involving a large independent physicians' association.
  • Represented an insurer in an R&W coverage dispute arising out of alleged breaches of financial and operational representations in connection with the acquisition of a U.S. property and casualty insurer.
  • Represented an insurer in a commercial crime coverage dispute arising from a complex fraud perpetrated on an international financial services firm.
  • Advised a carrier on financial institution policy coverage for claims involving lending/servicing conduct and supported related litigation posture.