A Royal Navy Commander drunkenly slapped a fellow officer's bottom so hard he left her buttock "sore", a court martial heard on Monday.

Steven Heap, who received an MBE from Prince Charles in 2013, had been drinking for several hours when he followed a fellow Commander onto the dance floor at a Navy base party and slapped her as she danced.

When the shocked woman allegedly fled and later returned to the dance floor, his right hand struck her backside a second time.

A court martial heard the 48-year-old accepts he slapped the senior officer's bottom, but claimed he was simply "joking about".

Heap, who was based at HMS Excellent in Portsmouth at the time, joined the Navy 30 years ago as a submariner and now works as a nuclear force inspector.

The court martial heard Heap had been at a Navy base Christmas party when he drunkenly slapped his alleged victim's bottom.

Prosecutor Wing Commander Michael Saunders told the court Heap initially approached the woman, who cannot be named for legal reasons, at the bar earlier in the evening.

Despite her allegedly wanting nothing to do with him, he then followed her to the dance floor and twice sexually assaulted her, the court heard.

The prosecutor said: "There was a function, which started at midday and lasted until late at night.