The 2,000m is 'on 10 mins'.
Reduce the 2,000m to a 1,500m (still on 10 mins) if it suits better.

Run from the Pillars to the 750m mark, then 500m back towards the Pillars and then 250m to return. The tempo of each set picks up as the distance of the rep decreases. Complete three sets in total. 
Recovery: start on 4.30, 7.45 and 11.00.  
[Alternate session: skip the last set or scale it back e.g. finish with 2 x 500m or 2 x 250m.]

Start at the 3.5km marker of the Tan.  Run anti-clockwise to the 2km marker around the back of the tan. Then on 8 mins return to the 3.5km marker for the second rep. Repeat. 
Option: adjust number of reps to suit your schedule or reduce distance of last two reps.

Meet at the Pillars, cross the road and do an out and back three stage progressive along the river, towards Richmond. 
*Stage One is 8 minutes along the river at a steady/brisk pace. Stage Two is 8 minutes at tempo pace (turning halfway, so after 12 minutes of total running). Stage Three is returning to the start at a fast pace (so much quicker than 8 mins).