In other words, very difficult.
Solution in post #40.
18 across is Makruk.
Good!
13 down is Lasker.
Lasker is right.
12 down is Gold.
2 down is Groningen.
Gold & Groningen correct!
14 across is Platov.
Right!
8 down is Capablanca.
16 across is en prise
Both correct!
10d Hubner
Hubner is correct!
6a windmill
11d tennis
Windmill & tennis both right!
15 a Neville
In other words, very difficult.
Solution in post #40.