Arrived off Rio today, and connections didn't look too bad, so I thought I'd give it a go.

6m30 to get from conformance to passports
9m30 to get from passports to the start of "fast track" security

The acutal xray process was fine, just under 4 minutes from starting to empty my bags to finishing collecting them. Total trays stacked thanks to lazy people: 7, plus my 4.

Total time from conformance to end of security: 19m49.

After conformance I noticed that the e-passport booths were completely empty, and I suspect I could have saved 10 minutes by going landside.

Skipping the domestic connection process (i.e transferring internationally) would have saved about 7 minutes, so 13 minutes end-to-end, with fast track. Without fast track the queues were horrendous.

Comparison to Rio security:

Rio: Laptops in bag, liquids in bag, electronics in bag. Belt off.
Heathrow: Laptops out, Ipad out, liquids out, bag of electronics out, other bag of electronics out, belt off.

However Rio then had a 40 minute wait to be allowed out of the country with departure passport controls, something that the UK and US do right and most countries do wrong.