I have used Tim Harris's approach for years. It is called "CPES" Clear Penetrating Epoxy Sealer". Not sure what they call it in the UK. But a Marine Chandler will know about this stuff. But as somebody on TalkMorgan pointed out this looks like the "Tip Of The Iceberg". I have repaired structural damage that was worse than the picture. But I am thrifty (cheap) and I try to catch this stuff before it gets to be major. I have used Epoxy Putty to rebuild pieces of wood and painted them so one really would not know I had used this approach. You will hear over and over, "If You Are Going To Do It Do It Right". Yea and have money to burn also.
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Seattle