We started the game nervously, and conceded posession far too often, but despite Marseilles looking dangerous in their build up play, they didn't threaten our goal on too many occasions.
You'd have to say that 0-0 at half time was a fair reflection of the play - we weren't able to penetrate their defence despite occasional flashes of magic from Wilshere and Ozil.
The second half was a different story - a shocking error gave Theo the chance to blast the ball past their keeper for the opener, and a Merson-like run from Ramsey made it two-nothing.
Marseilles won a very dubious penalty in injury time - Ramsey clearly got to the ball, and there looked to be no contact with their man whatsoever. No matter - it was too little too late for the French, and we have the ideal start to the campaign.
This was out 10th successive away win, and thoroughly deserved.
Here's the report from Sporting Life:
Arsenal may have ridden their luck at times but Arsene Wenger will not mind after seeing his injury-hit side get their Champions League campaign off to a winning start in Marseille - their 10th successive win on the road.
Wenger had claimed the quintent of Marseille, Rafael Benitez's Napoli and last year's runners-up Borussia Dortmund made Group F the hardest of this year's competition.
The Frenchman also conceded that unless their injury situation improved - currently eight first-team squad members are out - then they would struggle to make it out of the group for the first time since the 1999/2000 season.
Wenger will therefore have been all the more relieved to see his side pick up yet another win on the road this evening on the French south coast.
Theo Walcott and Aaron Ramsey's second-half strikes proved the difference at the half-finished Stade Velodrome, where the hosts dominated for large periods of the match.
Marseille, back in the competition after a year's absence, edged the first half, with Andre Ayew and Andre-Pierre Gignac coming closest.
Rod Fanni was inches away from grabbing the opener moments into the second half, before Kieran Gibbs saved Per Mertesacker's blushes by clearing his miskick off the line as Gignac waited to nod into an empty net.
It was a moment that proved decisive as another defensive mistake at the other end put Arsenal in the driving seat.
Jeremy Morel misread a Gibbs cross, allowing Walcott time to rifle into the roof of the net and quieten those who had criticised his finishing in Saturday's 3-1 win at Sunderland.
The hosts pressed hard for a leveller but Ramsey's low strike seven minutes from time put the game out of reach for the hosts, who pulled one back through substitute Jordan Ayew's stoppage-time penalty.
Source: Arsenal World