You Do Need power plug adapter while traveling from Great Britain to Denmark.

Here is Why You Need An Adapter

The outlet and plug type used in Denmark are C, E, F and K and in Great Britain is G. This is how they look like.

Great Britain

In Great Britain, outlets of type G are in use.

Type G

Denmark

In Denmark, outlets of type C, E, F and K are in use.

Type C

Type E

Type F

Type K