Webb entered Parliament in 1695 as Tory Member of Parliament for Ludgershall, and became a close political follower of St John. In the same year, he was promoted to Colonel of Princess Anne of Denmark's Regiment of Foot in 1695. In September 1697, Webb was dangerously injured in a duel. The following year he briefly lost his seat in Parliament, but his defeat at Ludgershall was overturned on petition. He served in Flanders in the campaign of 1702-1703, was a Brigadier at the Battle of Blenheim and a Major-General at Ramillies and Oudenarde.