Well...the protophane should last about 15 hours and acts as your basal level of insulin would if you were still producing your own insulin. The purpose of long acting insulin such as Protophane is to cover blood sugar rises during the fasting state (overnight and between meals). The Novorapid only lasts for about 5 hours and starts working in about 20 minutes.
No, I wouldn't expect the Novorapid to keep you at 4.5 for 3 hours, but with the Protophane and the Novorapid combined, neither would I expect to see it jumping well over 200 unless the dosage needed adjusting or you were eating more carbs than your insulin could cover. It could also be that your body is neutralizing more of the long acting (or short acting) insulin than anticipated; Dr. B suggests that anything over 6 units at one site at one time causes the body to neutralize quite of bit of the extra dose and if you need more than 6 units to split the injection into 2 or more sites.
Something else that Dr. B mentioned is that warmer weather (it is summer down there right now, right?) requires higher insulin doses.