Place the ham in a roasting dish with 1 cup water in the bottom of the dish. Roast for 1 hour and 15 minutes. (Check the ham after 45 minutes and add more water if necessary or tent with aluminum foil if it is getting past a dark golden brown.)
Meanwhile, combine the syrup, mustard, soy sauce, brown sugar, vinegar, Worcestershire and cayenne in a saucepan over medium-high heat. Cook, stirring frequently, until the mixture is thick and bubbly, 15 to 20 minutes.
If you used it, remove the foil from the ham and slather the ham with the glaze. Return the ham to the oven uncovered. Continue to roast, brushing the ham with the glaze every 15 minutes, until the internal temperature is between 140 and 150 degrees F, another 1 hour and 30 minutes. (If the ham starts to become too dark on the outside, tent it with aluminum foil. We are looking for a dark, sticky, flavorful glaze on the outside of the ham. Use all the glaze! Really slather it on!)
Remove the ham from the oven, remove the foil, brush with any remaining glaze and cook, uncovered for another 5 minutes. Let it rest for 20 to 30 minutes.