The personnel of the Women's Royal Naval Service, part of the British Royal Navy, are known as Wrens (from WRNS). The WRNS was abolished when women were integrated into the regular navy in the 1990s.
The WRNS uniform is regarded as being among the most attractive of women's military uniforms. Note the buttons done up on the left side. During World-War II, WRNS uniforms had blue insignia rather than the gold as seen here.