Dear Rabbi Simon,
Can you bring and eat your own kosher food at a work team lunch taking place in a non-Kosher restaurant?
This is disputed among the posekim, partly based on the question of whether we are concerned for new מראית עין (ie presumption of impropriety on the part of an onlooker) scenarios or are we only bound by those mentioned in the Talmud (Peri Toar vs. Peri Hadash YD 87). Rav Moshe Feinstein (OH 2:40) was very reluctant to allow eating [kosher food] in a non-kosher establishment, however others seem prepared to rely on the Peri Hadash above. In a situation of need (eg work/business context) it has been suggested that you leave some packaging or similar next to your plate so that a hypothetical onlooker will realise that you are eating your own food, not that supplied by the restaurant. I would go with that במקום צורך (in a situation of need).
Rabbi Rashi Simon