What is the difference between a s20 non-fatal offence against the person and a s18 offence?

One main difference between a s20 and s18 offence concerns the mens rea, or 'mental state', of the defendant. For a s20 offence, the defendant must intentionally or recklessly wound or inflict grievous bodily harm on the victim. On the other hand, for a s18 offence, only a clear intention to wound, inflict GBH or resist or prevent a lawful arrest will be sufficient mens rea. Consequently the main difference here is that recklessness will not be sufficient for a s18 offence, but it will for a s20 offence. As a result, we can see that s18 is a much more serious crime as it requires an actual intention rather than recklessness. This is reflected in the fact that the maximum sentence for a s20 offence is imprisonment for 5 years whereas for a s18, a life sentence is possible.Another difference is that both sections create separate offences. For example, s20 Offences Against the Person Act creates 2 potential offences: 1. Intentionally or recklessly wounding another, 2. Intentionally or recklessly causing GBH to another. Alternatively, s18 OAPA creates 4 separate offences: 1. Wounding with intent to cause GBH 2. Causing GBH with intent to cause GBH 3. Wounding with intent to resist/prevent lawful arrest 4. Causing GBH with intent to resist/prevent lawful arrest. This shows that s18 both widens and narrows the scope of the offence as the mens rea requirement includes intention to resist or prevent lawful arrest, increasing the scope of liability. However, by excluding the recklessness element it also narrows the offence to exclude liability in certain cases.