I have applied this year, so here's the info you need
They don't give out offers, you get points based on your A-level grades and an extra test called the HPAT, and if you're above a cutoff, you get a place on results day. your A-level grades are out of 565, and HPAT out of 300, and for Trinity last year you needed 739 points, so the higher you get in the HPAT the less you need from your A-levels.
A* at A level are 150 points, As are 135, Bs 120 etc. You also get 25 extra points for A level maths.
After yo have reached 550 points from your grades, every 5 points you get actually count for 1, so for e.g. if I get 580 points, that gets scaled down to 556.
You then add your HPAT score onto your points from grades. Although they don't say you need 4A2s, to get enough points you definitely need them.
For example: I got 191/300 in the HPAT, and from grades I will most likely get A*maths ABB - 550 points so overall 741 points, which would have got me into Trinity last year, but unlikely this year as points go up around 8 each year
Any more questions, just ask