Thanks for the response. I am not sure that the WIKI is accurate then:

11.2) For cancellations

For cancellations and / or when you are rerouted on to another service, some shorter delays attract a half rate payment. If the reroute involves departing less than an hour early, AND arriving less than 2 hours late at the original destination airport, there is no compensation, no matter what (Regulation 5.1.c.iii). The following diagrams explain what happens if the delay is longer and/or you need to leave more than an hour early.

The graphic that follows then has compensation due for 0:00 to 2:00 late.

I must be mis-understanding what it says.


Edited to Add:

The actual wording of the regulations is

1. Where reference is made to this Article, passengers shall receive compensation amounting to:
(a) EUR 250 for all flights of 1500 kilometres or less;
(b) EUR 400 for all intra-Community flights of more than 1500 kilometres, and for all other flights between 1500 and 3500 kilometres;
(c) EUR 600 for all flights not falling under (a) or (b).

In determining the distance, the basis shall be the last destination at which the denial of boarding or cancellation will delay the passenger's arrival after the scheduled time.

2. When passengers are offered re-routing to their final destination on an alternative flight pursuant to Article 8, the arrival time of which does not exceed the scheduled arrival time of the flight originally booked

(a) by two hours, in respect of all flights of 1500 kilometres or less; or
(b) by three hours, in respect of all intra-Community flights of more than 1500 kilometres and for all other flights between 1500 and 3500 kilometres; or
(c) by four hours, in respect of all flights not falling under (a) or (b),

the operating air carrier may reduce the compensation provided for in paragraph 1 by 50 %.

So 20 mins does not exceed 2 hours therefore the reduced compensation would be applicable. It appears the WIKI is correct.