Saute onion and celery in olive oil until translucent and softly-cooked, about 10 minutes.
Set aside.
Remove skins from potatoes and grate coarsely into a large bowl.
Add onion and celery.
In a small bowl, whisk together mayonnaise, egg, Worcestershire Sauce, thyme, capers and season to taste.
Add to potato mixture and stir until combined well.
Add salmon and incorporate evenly.
Form 1/3 cup measures of salmon mixture into patties and dredge in flour.
In a large skillet, heat butter and oil over medium-high heat until hot but not smoking, and saute patties in batches for 3 minutes pr side, or until golden-brown.
Serve salmon cakes with lemon wedges.
