Find the value

$=(1)^{3}-(3 a)^{3}$

$=(1-3 a)\left(1^{2}+1 \times 3 a+(3 a)^{2}\right)$

$\therefore\left[a^{3}-b^{3}=(a-b)\left(a^{2}+a b+b^{2}\right)\right]$

$=(1-3 a)\left(1^{2}+3 a+9 a^{2}\right)$

$\therefore 1-27 a^{3}=(1-3 a)\left(1^{2}+3 a+9 a^{2}\right)$