Many thanks for the quick replies. If these lights were just high up extra navigation lights, it will be an easy fix to just wire them up with the cabin navigation lights. A bit of a let-down really as I was about to try and program a pic integrated circuit to sent out some morse !! A very big learning curve, except that I used to send out morse code as an amateur radio operator in the past as G4ZSS. It will be easy to have a switched circuit to switch these extra mast head lights on/off.
Thanks for the interest I look forward to anymore comments,all the best, steve.

Hi Steve, This was the very first type of boat that I scratch built and thoroughly enjoyed making and sailing. Normally the navigation lights are perched atop the cabin roof, From your description, these lights are perched higher up and doubled which sounds to me as though they were meant to be seen at the height of battle. Also consider that an HDML is quite a low down boat and in open ocean they could easily disappear in deep wave troughs. So in conclusion my thought are that they were just extra lights to make them more visible in difficult circumstances. You also state that this HDML was a navigational leader therefore it needed to be visible.
Best wishes Tim.
P.S. Although John Lambert is considered an authority, I have been building Caldercraft's Sir Kay, I have discovered some discrepancies between his drawings and dockyard plans and photographs.

Now that's a tough one, but stumbled across these notes below...The last note is interesting. No mention of morse code. 🤔

A ship's masthead light shows that the ship is moving under power. At the bow you have forward/sideways arc red and green bow lights (port and starboard).

At the stern you have aft/sideways arc stern light.

This combination allows another ship at night to work out the direction the ship is moving.

The masthead light (forward/sideways arc) between the bow and stern lights and positioned higher shows that the ship is under power.

In addition, on top of the mast, are other red and white (360°) lights to show if the ship is fishing, towing, not under command or anchored.

One third the way up the front of the mast and facing forward/sideways is the 'masthead' light. At night if sailing only the tricolour is lit. If motoring the tricolour is unlit and the bow, masthead, and stern lights are lit.

My thought is that they don’t signal anything. They were just positioned like that to be visible to the other vessels as identification that the ship was a leader.

I am building a HDML at 1/24th scale from the model boats plans Jan/Feb 1984, and the Sarik vac formed hull. (Harbor Defence Motor Launch)
The model that I have finally decided on is ML1407,which took part on the D Day landings as a navigational leader.
According to the late John Lambert in the book Allied Coastal Forces of WW2 page 129, the boat was fitted out with extra radar-plus antennas, plenty of splinter mats and "fighting lights" which he gives more information on page 172 showing two red lights on the port side of the tee mast and two green lights on the stb side, as per normal navigation lights. What I need to know is how these lights were displayed. I have been advised by the Captain of HMS MEDUSA one of the only remaining HDMLs still sailing,I believe, that he thinks that these lights wouldn't have sent morse code. I presume they were there to avoid "friendly fire" so what the h*** did they display or flash !!!! Can anyone give me a correct answer. 🤓
The boat is near completion apart from fitting the radio and the wiring to the mast lights. Everybody that I have asked has no idea so please HELP..
I'm not on the computer very often so I apologize now if I don't reply quickly. Many thanks Steve.