John "Mad Jack" Fuller, like many wealthy landowners of his time, entered the political arena and sat for parliament. His cousin, Hans Sloane encouraged him to sit for Southampton in 1780. In 1796, Fuller was appointed High Sheriff of Sussex, for a period of one year, and in 1798, he raised a troop of Sussex Gentlemen and Yeomanry Cavalry. In 1801, Sir George Shiffner, Fuller's cousin's husband, invited him to stand for Sussex.
"People along the roads must have been quite amazed as they saw the Fuller family-barouche drive through the muddy country lanes of Sussex: a coach drawn by four large horses, the coachman heavily armed and accompanied by footmen also wearing pistols an swords, and the whole coach filled with provisions as if as someone wrote, they set out for an Arctic journey. It was probably because of the fact that he Fuller arms were painted on the coach that people weren’t deluded into thinking that the carriage contained the prince of Wales en route from Brighton to London. Another sign that Fuller wasn’t wholly in touch with the times ( one of the most important and striking things about eccentricity) was his hair dress - he powdered his hair and wore it behind in a so-called pigtail [long after it had gone out of fashion]." Fuller Hath Done a Very Great Thing: ‘Mad Jack’ Fuller and His Follies, Wim Meulenkamp, p 38.
The most colourful chapter of Fuller’s political career opened with his participation in an enquiry into the Walcheren Expedition where the British troops suffered heavy losses in the Netherlands. It ended in Fuller being taken into the custody of the Serjeant-at-arms and public disgrace.
There were many Members of Parliament in Jack Fuller's family including: his cousins Hans Sloane (1739-1837) & General Sir Augustus Elliot Fuller (1777 - 1857); uncle Rose Fuller (1708 -1777); his grandfather John Fuller (1680-1745) and his great-grandfather Major John Fuller (1652 - 1722).
Given Fuller's ebullient and obstreperous personality, it is not surprising that he was considered a "character" in the House of Commons and got involved with more than one heated exchange. It is said that he rode from Rose Hill, his home in Brightling, Sussex to Westminster in grand style.